Not long ago, the professional music industry involved a complex but fixed set of players: artists, labels, managers, promoters and the like. Many of these roles have changed, but none have disappeared. They're joined by a new set of participants: tech giants, streaming services, social music startups and, perhaps most crucially, developers.

This weekend, coders and industry representatives gathered in San Francisco for Music Hack Day, a tradition that has spanned continents for the last four years. Like other hack days and hackathons, the event is dedicated to bringing developers together to build new things using the latest technologies and platforms. In this case, the focus is on music, so the toolkit includes everything from mobile hardware and homemade digital instruments to open Web standards and the APIs of services like SoundCloud, Last.fm, Spotify and the Echo Nest.

Noteworthy hacks conjured up in the past have included various software mashups between services, as well as things like invisible, interactive instruments that can be played in the air or on a surface. Some hacks are strictly Web or software-based, while others involve some tinkering with hardware, including LED lights, Nintendo Wii controllers and Kinects.

The most recent Music Hack Day spawned a total of 62 hacks. The list included a music search engine that queries multiple streaming services, as well as a Theramin made from two iPhones. One app succeeded in predicting Sunday's Grammy winners almost as effectively as Billboard did.

Some creations were simpler, such as a Spotify-based clone of the classic MP3 player WinAmp, a mash-up between iTunes and the Echo Nest's recommendation engine and a SoundCloud plugin for Wordpress.

The hacks ranged from the mind-blowing to the simplistic but useful. They dealt with everything from the creation of music to its distribution and promotion.

How Music Hack Day Helps the Music Industry Evolve

Music Hack Day was started in 2008 and hasn't stopped growing since. In the tradition of other hacking events, SoundCloud VP of Business Development David Haynes teamed up with experienced hack day organizer James Darling to create a music-specific event. The proliferation of APIs from various music-related platforms plus some of the other disruption going on in the music industry made the space ripe for some creative hacking.

"Weren't sure what to expect from it at first," said SoundCloud cofounder and CTO Eric Wahlforss. "It got off to such a good start that's now become sort of a tradition for the last few years. Music Hack Day is a big part of our culture."

For startups like SoundCloud, events like Music Hack Day yield creations that could one day find themselves integrated with the company's core product. The vast majority, however, will not. And that's okay. The event's value is of a much deeper nature, in that it fosters a developer community around music and brings a wide range of players into the same, from independent coders to music industry representatives.

A side effect of this type of collaboration is that the entire industry is creeping forward. A few years ago, Wahlforss told us, some record labels had no idea what an API was or how it was relevant to their business. Today, EMI has an API of their own. They, along with Universal Music Group, participate in Music Hack Day and are curious about much of the fruit it bears.

"If you speak to the labels today, they're all about API's and mashability of their content," Wahlforss said. "They're very on board with this trend, which is very exciting to see."

For SoundCloud, this spirit of hacking is something that plays a prominent role in the culture of the company and its growing team of developers. Modeled after Google's "20% time," the company encourages employees to use what it calls Hacker Time to experiment and build new things that may or may have any direct bearing on the official product strategy for SoundCloud.

The company also recently hired its first developer evangelist and is silently preparing a major announcement about its platform.

Pushing Music into the Future

SoundCloud isn't the only company pushing the boundaries of what's possible in online music. Innovation is all over the place, from Spotify's new third party app platform to the long and growing list of apps powered by the APIs from services like The Echo Nest, Last.fm, Bandcamp and several dozen others.

The open architecture of the Web, the proliferation of APIs and hacker culture have already made a notable mark on how people create, discover and share music, yet all of this is still very much in its earliest stages.

Twenty years from now, things will look even more different. The industry and ecosystem will move forward together, probably with a few players becoming obsolete along the way. Artists and sound engineers may lead the creative charge, but if what emerges looks and works radically different from what we have today, we'll have developers to thank as well.

Music Hack Day Photo by Thomas Bonte

The new player first went into beta in November, giving those curious enough an opportunity to experiment with it. Now that the bugs have been ironed out and a few new features added, the widget is ready for prime time.

A big part of that growth, cofounder Alex Liung told us, is the company's mobile strategy. It has highly functional native apps for iOS and Android, but the browser-based Web is another story. When users try to play back embedded SoundCloud clips on an iPad or iPhone, the old player simply wouldn't work, like all the other Flash embeds scattered across the Web.

HTML5: A Necessary Move

For this reason, the conversion to an HTML5 embeddable player is a necessity for a service like SoundCloud if it expects to maximize its reach across the Web and keep growing. Flash will presumably never be supported on iOS devices iPads and iPhones, a fact that wouldn't matter so much if Apple didn't keep selling millions upon millions of them. Just last quarter, over 15 million iPads and 37 million iPhones landed in the hands of consumers, and this revolution in personal computing is still well underway. In November, Adobe announced that it would suspend development of the mobile version of Flash, apparently accepting that open standards like HTML5 and related technologies could do most of what Flash was capable of it.

It's not just cross-device compatibility that makes ditching Flash a good idea. HTML5 is also less resource-intensive when playing back audio, and should exhibit better performance.

While testing the new player out, the SoundCloud team discovered a few other advantages as well. Apparently, the appearance of the revised player made users twice as likely to hit the "play" button. From there, they were eight times more likely to share a given track with others.

Now that it's coming out of beta, the new player now supports saving any sound to one's "likes" and making comments in-line on the waveform, which was one of more the powerful features of the original Flash player.

To celebrate the milestone, the four-year-old startup has released an audio slideshow storytelling app called Story Wheel. It uses the Instagram API to grab a set of pictures, from which you can select the ones you want and order them. Once the photos are arranged, a brief narrative can be recorded in the browser. The end result is a shareable photo slideshow annotated by you.

The service's growth has also been fueled by the proliferation of its mobile apps and open platform for developers, Liung told us. More than 10,000 third party apps are being developed on SoundCloud's platform, something that has a way of naturally extending the service's reach across the Web.

Perhaps more significantly, SoundCloud's availability on iOS and Android has made the service more accessible and portable. It's easy to see why that's the case. Users can record audio directly into their iPhone, iPad or Android device and publish it to SoundCloud from within the app. On the other end of the equation, listening to audio from SoundCloud on mobile devices is as straightforward as using an iPod or the mobile version of a streaming service like Spotify. For users who actively follow others, SoundCloud can be used as a mix tape comprised largely of content that isn't available on other services.

What's Next For SoundCloud: HTML5 and Social Audio

We asked Liung what SoundCloud is focusing on next. For his team, converting its default embeddable player to HTML5 is a high priority. They launched an optional beta player in HTML5 in November and are in the process of making that the service's default player. Projects like this become a necessity for any company that wants its service to work flawlessly across devices, especially Apple's notoriously anti-Flash iOS platform. SoundCloud's native iOS app has done quite well, but it's all those audio files embedded across the Web that have trouble playing back on iPads and iPhones.

SoundCloud is already an inherently social service, but further injecting itself into the larger social Web is another top priority for the company. SoundCloud recently jumped on the "frictionless sharing" bandwagon with a deep Facebook integration. As controversial as this semi-automated model of sharing is, it has nonetheless proven to be a source of major growth for sites and services who get onboard, thanks to Facebook's massive user base.

Digital music only continues to grow and mature, as streaming services explode, Internet radio companies go public and developers begin using the power of open APIs to mash up sounds and services. SoundCloud alone saw 231% growth last year, while Twitter saw a 104% increase in music-related activity.

What's interesting, though, is how the Web is paving the way for unsigned, independent artists to reach levels of popularity that rival major label acts. This is especially true on SoundCloud, where unsigned artists flock to upload their recordings. But even across the larger Web, three unsigned artists broke into Next Big Sound's "Social 50" list, which chronicles, the 50 biggest artists across all of the social and music sites that they track.

These numbers, while impressive, should be taken with a grain of salt. Next Big Sound has gone to great lengths to pull data from sources like YouTube, Rdio, Last.fm, Pandora, SoundCloud and several others. One service missing from their list is Spotify, which just launched in the U.S. this past summer and has seen enormous growth since then. Still, it looks like they're using a pretty hefty sample of online music data to draw their conclusions. You can take a closer look at their methodology. if you're curious.

Berlin based music and audio sharing network SoundCloud has raised a reported $50m more venture capital from the super prestigious Kleiner Perkins Caufield & Byers, Mike Butcher at TechCrunch Europe reported today. The company had raised about $16m in two previous rounds. If you're not familiar with SoundCloud, now is a good time to learn about the site. It's a vibrant and innovative community, about to either blow up huge or go down in flames with the change that comes from a large and high-priced investment like this.

Meeker's 2011 presentation on the state of the internet addressed a trend of companies growing strong in one small market and then exploding out onto the global stage; she provided 4 examples of that trend and SoundCloud was the only one of the four not yet a Kleiner portfolio company. (Waze, Shazam and Spotify were the others.) Meeker also mentioned SoundCloud in discussing her belief that sound is going to be a next major area of innovation, eg. Siri, Spotify and SoundCloud.

Meeker loves mobile and while SoundCloud's mobile apps are already good, it will be interesting to see whether and how her leadership inspires further development in global mobile applications.

What SoundCloud Means

SoundCloud is an inspiring community of audio producers and fans, leveraging new technology like widespread smart phones, cheap data storage and transfer, within a great user experience. It's reminiscent of the best things about YouTube in its early days, but it's different.

One good way to get started finding good things on SoundCloud is via the official staff collection of highlights from the site. That's where I found the WildEarthVoices account, whose recordings and favorites from other accounts are all about ambient sound recordings from nature. SoundCloud has all kinds of sounds on it though; from podcasts to thunderstorms to electronic music, music made electronically and music you might call electronica. (There's a lot of electronic music on SoundCloud.)

Not all of SoundCloud's experiments work out either, SoundCloudLabs was an effort to highlight cutting edge apps that seems to have lost steam over the past Summer.

None the less, the SoundCloud community appears to be small but growing fast. Traffic analyst firm Compete reports 2.3 million unique visitors per month, up nearly 2X year over year. SoundCloud self-reported 5 million registered users in June. It grew to 9 million as 2011 drew to a close. Pandora, for context, has 80 million registered users.

The company only added web and iOS one-click recording at the end of 2010. The acclaimed iPad app came out in October. The website still doesn't offer RSS feeds of published files.

There's something really exciting about checking the Activity stream on the SoundCloud iOS app and finding something new, then clicking through to listen with other people to music that was just posted.

SoundCloud was founded five years ago this month by CTO Eric Wahlforss, who has degrees in Philosophy, Industrial Economics, Computer Science and Business Administration and CEO Alexander Ljung, who studied marketing and Human Computer Interaction. Both are Swedish. ReadWriteWeb founder Richard MacManus did an in-depth interview with Ljung about the company's prospects this October.

From inline commenting to smooth integration with 3rd party social networks, the user experience at SoundCloud is fun. Discovery can be a little challenging but exploration is easy. It would be nice if SoundCloud would sync with my Scrobbled musical history at Last.fm and offer me immediate personal recommendations.

AnnoySPASMcrack by ellefläädt

The service hosts up to 120 minutes of audio for free, then offers annual subscriptions for more storage, advanced analytics and promotional materials priced at between €29 ($37) per year through €59 ($76) per month for the unlimited pro plus package.

The site offers a huge quantity of Creative Commons licensed audio and loves to interview the users of that and other content.

The SoundCloud API supports an app gallery with more than 250 apps listed and probably an even larger array of independent projects, from things like urban music catalogue CitySounds.fm to the collaborative mashup art project Instagrambient.

SoundCloud feels like the kind of creative place that the Internet was meant to be. For that to gain a big infusion of cash and the support of some of the world's leading tech investors will hopefully mean more of the same and even better for the SoundCloud community.

Until now, the SoundCloud player, like so many of its kind, was built in Flash. The service has native apps for Android and iOS, which are lovely, but not terribly useful when one stumbles across a sound clip embedded on a Web page while browsing from an iPad or iPhone.

The advantages of this new widget go beyond cross-device compatibility, although that's certainly a huge one. Because it doesn't rely on clunky, proprietary Flash technology, it should be faster and less resource-intensive to playback audio this way. It also provides for more speedy development moving forward.

The new widget has a long way to go before becoming the default player, but this first iteration is pretty impressive overall. It even supports time-based commenting within the audio waveform like the standard player.

SoundCloud is just the latest company to jump on the HTML5 bandwagon, recognizing that tablets and smartphones are only going to continue to proliferate and to stay competitive, companies that specialize in Web content that used to depend on Flash need to adopt the new standard as soon as they can.

The service has had its own native apps for Android and iPhone for awhile, and just launched an iPad app last week.

Most of the functionality from the service's Web app is here. If you've seen the SoundCloud Mac App for the desktop, this is a very similar experience.

The app can be used to actively discover and listen to music and audio clips in short bursts or can provide more of a "lean back" experience for sound, functioning as a sort of digital mix tape to listen to in the background.

Read/Write Sound: The iPad as a Content Creation Device

When the first iPad launched in early 2010, one of the biggest criticisms leveled against it was that it was too heavily geared toward passive consumption of content, and lacked many of the participatory features of the Web. As the iOS platform has evolved and Apple has updated the hardware to include a camera, the iPad has grown into more of a read/write device.

Just as other iPad apps allow for the creation and publication of text, photos and video, Soundcloud lets you record and publish snippets of audio from the device. In the process, you can share it on Twitter, Tumblr or Facebook, including any brand pages your Facebook account has administrative access to.

In addition to posting audio clips, users can interact with others by commenting on individual sound files. Those comments can be added at specific points in the audio waveform, just like on the service's website.

The result is an app that lets users discover more obscure, independent and often homemade music, rather than a catalogue of music that's only been formally released by record labels. That's because SoundCloud hosts mostly user-generated music, including covers, mashups and original compositions. Some more established artists and labels have even embraced Soundcloud and uploaded commercially released albums to the service. It's essentially the YouTube of audio.

Surpisingly, tapping a song that you find via an artist search does not initiate a recomendation-based station like Pandora or Last.fm. Instead, it adds it to your personalized station. The recommendations come into play earlier in the search process. A search for "The Flaming Lips" returns music by that band, as well as several acts that are deemed similar by Last.fm's data.

Since the content on SoundCloud is so varied - some artists have full albums, some have 30-second clips, while others have only remixes, mashups and covers - the experience of using the app can be a bit varied as well. On the whole, it's a pretty effective way to discover new music beyond the large but inherintly limited catalogs of streaming services like Spotify, Mog and Rdio.

A Different Kind of Mash-Up: APIs Fuel Music 2.0

If nothing else, this is a creative fusion of two APIs from different music services that results in a new music-listening experience. It's the same kind of data mash-up we've seen on a variety of projects that utilize the massive Echo Nest music recommendation data set. For example, one developer created a recommendation engine for Spotify, which is a feature sorely lacking from the popular music streaming service.

Developers have been using the Last.fm API for years to build all kinds of new mashups and apps for discovering and listening to music.

Immediately after Meeker's presentation, I sat down with SoundCloud's young co-founder and CEO Alexander Ljung. I wanted to find out just how Ljung and the SoundCloud team plan to take their service to the mainstream.

SoundCloud's Exponential Growth

Ljung described SoundCloud as "a platform to enable anybody to create and share sounds." The service was built in Ljung's native Germany and launched at the end of 2008.

SoundCloud had "steady exponential growth from the start," Ljung said, citing about 7.5 million users now. About 5 million of those signed up in the past 12 months.

At last month's Facebook F8 event, SoundCloud launched its latest big feature: deep integration into Facebook's new design. It has also been busy partnering with other services, such as integration into a music-making desktop app called Cakewalk.

But How Will SoundCloud Go Really Big?

Despite SoundCloud's impressive growth, it will need to find a way to bring in many more millions of users in order to go mainstream.

SoundCloud's vision is certainly big. "Sound is more than just music," said Ljung. Although, music was where the initial traction came from on SoundCloud - musicians uploading demos, mashups and even entire albums.

I pointed out that the biggest audio publishing trend so far on the Web - podcasting - hasn't gone mainstream. At least not at the scale of online video. So, I asked Ljung how SoundCloud plans to get more people to upload and consume audio on the Web.

He replied that podcasting is a specific delivery format and it "somehow set the rules" that podcasts should be relatively long and professionally created. Which created "too high of a barrier" for many people.

However, the proliferation of smartphones, with their high quality microphones and recording apps (like SoundCloud), has led to an increase of short-form audio. It's opened up online audio to more casual users.

Consumption & Sharing of Audio

SoundCloud never wanted to be just another podcasting platform, but (in Ljung's words) to be "sound sharing the way it should've been." SoundCloud users can - and do - upload any form of audio to the Web, from music demos to 1-2 minute soliloques and even snippets of phone conversations.

To get to the level of YouTube, though, there will need to be a huge increase in consumption of SoundCloud content. The Facebook partnership, along with integration into other discovery platforms, is going to be crucial. But Ljung stressed that the SoundCloud platform itself already encourages its users to interact with content.

Each sound recording has a visual timeline bar and people can leave comments anywhere on the timeline. For example, at the 1:05 mark of a five minute recording, there may be a particularly striking piece of audio which attracted a lot of comments. So you might want to only listen to that specific part of the recording.

Only time will tell whether SoundCloud can really make it big, but its exponential growth so far has been impressive. And it's a great product. I use it regularly to listen to music, although I haven't yet fully explored its other use cases. Have you used SoundCloud? Let us know in our comments whether you think it will go to the next level.

Storify launched its public beta version in April of this year, and quickly became a popular platform for online content curation. Storify allows users to pull information from social media - tweets, videos, photos, links - in order to build stories, and SoundCloud is a smart, seamless way to add original music to the stream. It's an easy way to stitch together a diverse array of content into a news stream, a homeknit story, or just a curious experiment, like the aggregated nyan cat content below.

To add SoundCloud as a source in your Storify account, just go to Settings, Sources, and then drag the SoundCloud icon onto the Source bar. As you're building your story, just search for clips on SoundCloud.

The social audio-sharing site experienced several hours of intermittent downtime yesterday as SoundCloud's engineers fought off the attack.

Just the day before, the site experienced similar downtime issues, although it isn't clear if that was related to the DDoS attack or not. In terms of a motive for the attack, it was likely just the thrill of bringing down an increasingly popular service, rather than the fulfillment of some ideological agenda as we've seen in the past with Anonymous and Wikileaks-related DDoS attacks.

As of today, the site appears to be loading and operating without issues.

SoundCloud was founded in Berlin in 2008 as a social networking site primarily for musicians to share and promote their music. It has since grown into an audio-sharing platform for amateur and professional musicians alike, as well as podcasts and other audio snippets. In short, it does for audio what YouTube does for video, albeit on a smaller scale.

The Next Web's Drew Olanoff says "it's a similar listening and chat experience to what you'd find on Turntable.fm" and while I can see why he'd say that, it doesn't feel that cool to me. It's one band, listeners are unable to listen to the full songs Update: apparently I was wrong about that and songs are available in full, there's no creative control on the part of DJs. But yes, you can listen together with people near you. Geographic proximity could be a cool addition to Turntable.fm, in fact.

What Blink-182 has done has interesting potential though and is worth a brief look. I think it falls short of creating the kind of experience that visitors will feel compelled to share with friends though. I like the idea of listening to music with people near me, but not this music and not short clips like this.

Below, poor Google Chrome got my location very, very wrong. I'm a long way from LA.

The first service we'll look at is a startup from Berlin, Germany, called SoundCloud. It's a platform to publish music and audio to the Web - and it's been experiencing rapid growth.

SoundCloud is being used by professional musicians and amateurs alike. It's also become a platform for other online music services, such as The Hype Machine and We Are Hunted.

Trending alternative pop singer Lykke Li has been using SoundCloud to publish songs from her upcoming new album, Wounded Rhymes. There are also remixes of Li's songs on her SoundCloud. Indeed, one of SoundCloud's best features is that it allows artists to collaborate with others - including their fans - on remixes. 50 Cent and R.E.M. have both launched remix contests recently using SoundCloud.

SoundCloud recently went over 3 million registered users. Given its growth and the fact that popular musicians are using it, is SoundCloud a threat to MySpace? I checked out Lykke Li's MySpace page and the most recent entry is a link to a new song she just posted to SoundCloud (not available on MySpace). That song has 58 comments, as at time of writing. So yes, SoundCloud is a threat to MySpace. SoundCloud is hosting popular new music, tthere is social commentary happening around that music, and the site is becoming increasingly popular.

What then of Fred Wilson's hope that other audio creativity will blossom on SoundCloud? Wilson recorded a podcast on SoundCloud recently to explain. He noted that "the web is still too quiet, there's not enough audio expression happening" - meaning podcasting, spoken word, even poetry.

In that podcast, Wilson defined SoundCloud as an "online platform for audio expression and sharing on the Web and mobile devices."

"What YouTube is for video," he said, "SoundCloud is for audio." (at the end of 2008, Wilson called SoundCloud "Flickr for Musicians," which indicates how the product has evolved since then: from a musician-focused service to a consumer-focused one that nevertheless still relies on musicians).

Wilson elaborated further in a comment in his blog: "I believe that mobile phones as recording devices and tablets as creation devices and "audio exhaust" from gaming are all game changers for audio creation and sharing."

I'm skeptical that podcasting or spoken word audio will ever become a widespread activity on the Web. The problem is that listening to podcasts and spoken word audio requires focus - it just doesn't fit into the fast-moving, multi-tasking media world we're all living in. Audio will most likely never be shared and curated on a mass scale, like video is on YouTube.

However, my guess is that SoundCloud won't even need the audio aspect. It's already got popular music acts like 50 Cent, R.E.M., Lykke Li, Foo Fighters and Deadmau5 using its service. And the platform is very impressive: the API being used by Hype Machine and others, widgets galore, over 100 apps hooked into it.

Do you use SoundCloud? I'm curious to hear your thoughts too on the audio creation aspect of the product, do you think that will pan out?

While no one is arguing that MySpace has lost its grip as one of the leading music and entertainment destination traffic generators, I disagree with Van Buskirk's choice in SoundCloud as the great equalizer.

Due to the service's ease-of-use and speed, SoundCloud is indeed one of the best file collaboration and music sharing sites. Quite simply, the site does everything right except help indie artists monetize. Meanwhile sites like Mix Match Music and Bandcamp provide solutions for bands to share AND monetize their products.

In particular, Bandcamp's execution is extremely elegant. As with MySpace, musicians upload their cover art, track listings, liner notes, lyrics and audio files. But Bandcamp adds four additional key features:

1. File Conversions: The site converts a single uploaded file into eight different formats to meet device and music player requirements.

2. Monetization: Bandcamp allows musicians to price their tracks and albums as they see fit. There is even the option to let fans decide prices on a sliding scale.

3. Sharing Tools: The service provides embeddable player widgets for Facebook, MySpace and a variety of 3rd party blogs.

4. Analytics: Perhaps most importantly, site analytics measure popular songs, track links and locate where files have been embedded. This means that musicians can search out their best advocates even if they're miles (and sites) apart.

While SoundCloud is definitely a fantastic tool for collaboration and remixing, it's the storefront-style tools like Bandcamp that will either eat or be eaten by MySpace Music. We'll just have to see where the major artists choose to flock in the coming months.

CORRECTION: Earlier the writer described SoundCloud as a P2P site. SoundCloud is not structurally based on a peer-to-peer network of nodes. Instead the company considers itself a "Flickr for audio".

2. Deezer: Deezer offers users free and legal streaming music while sharing advertising revenue with artists and rights owners. The site launched with a Sony BMG partnership and signed a Universal Music deal in 2008. Users can share their favorite music by connecting with friends within the social network, or embedding playlists in 3rd party sites.

3. Spotify: Heralded as one of the best music streaming experiences on the market, Spotify is only available in the UK, Sweden, Norway, Spain, France and Finland. TechDigest TV uploaded a fantastic looking preview of Spotify's much anticipated iPhone app.

4. Tunerec: Swedish company Tunerec allows users to create music libraries and playlists from recorded radio play. Because libraries are taken from recorded music, it takes a while to populate playlists; however, according to RWW's initial review by Frederic Lardinois, the service is worth the wait.

5. Last.FM: If you haven't heard of Last.FM, you've probably been living under a rock. The site offers users the ability to create radio stations and stream them complete with AudioScrobbler-powered recommendations.

6. Pandora: To the user, Pandora and Last.FM are similar recommendation-based radio services; however, where AudioScrobbler makes statistical inferences, Pandora's recommendations are determined by the Music Genome Project's 400 distinct musical characteristics.

7. Slacker: Slacker is another popular radio recommendation service. Users input tracks and receive recommendations. Slacker first launched with custom mobile hardware and has since expanded onto other mobile devices.

8. The Hype Machine: This is a fantastic service for those willing to leave music selection to the experts. Like other sites, this one allows listeners to search for music and stream playlists; however, the files on the site are actually streamed from the blogs of top labels, DJs, promoters and music start ups.

9. Blip.fm: Blip.fm is another site where music lovers can access millions of streaming songs. Members receive their own station and the ability to share station programming responsibilities with friends. The site also offers integration with blogs, Twitter, FriendFeed and Last.fm. The act of blipping refers to the act of linking to a song and attaching a 150 character comment to it.

10. MOG: MOG is a music blog network that encompasses more than 300 blog posts per week. The site offers an in-depth look at new artists and includes music recommendations, videos and streaming audio clips. A good place to start with this service is to play audio from it's Recently Popular Posts page.

11. Lala: Lala also offers users a playable web browser interface. The service contains 7 million free online songs and the ability to purchase additional web songs at 10 cents each or downloadable MP3's for 80 cents and up each.

12. Imeem: Imeem is considered "the new social mixtape". The streaming music site allows users to create playlists and share them across the web. RWW recently covered Imeem's iPhone and Android launch.

13. SoundCloud: SoundCloud also allows users to upload tracks and share them via the cloud. Listeners receive shared files via an email-style interface. From there, they can choose to either play the music from the site or download the tracks they've received from friends.

14. 8Tracks: This service lets users upload 8 tracks as a playlist and share the playlist with friends. This service is essentially what Muxtape used to be.

15. Muxtape: Muxtape has transformed from one of the early mixtape-style music sites (users uploaded and shared playlists) to a directory of bands. It remains a great place to discover indie bands.

16. Project Playlist: Project Playlist indexes music from across the web. Again, users create playlists and share links to music files with their friends. Reviewers see this as one of the best music search engines in existence.

17. Skreemr: Skreemr is also a search engine and music indexing site. It claims to offer users access to "6 million mp3 files from over 100,000 web sites".

18. Fizy: Similar to the now defunct Seeqpod, Fizy is an extremely bare bones approach to streaming music with a simple search bar. Like Seeqpod, the site offers speedy music video results and audio results, and unfortunately, legally questionable content. Perhaps the site's recent acquisition will change that.

On the Horizon: Microsoft is set to launch a streaming music site at the end of July. For more info on this project check out our coverage.