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How big is social media these days? Big enough to get its own week. This week is Social Media Week, if you hadn't heard, and its taking place in nine cities across the globe. It's a week-long extravaganza of free (or cheap) talks, roundtables, panels, happy hours and other events and we thought we would take a look and give our top five, must-attend events of the week.

Social Media Week is already in full swing, so if you're just getting started now, you've already missed out on a few must-see events, but there's still several days left, so fret not.

Salesforce.com is a cloud computing company but when it comes to work, San Francisco is its home.

CEO Marc Benioff is a native of San Francisco. He has donated $100 million to the University of San Francisco Children's Hospital. Now, the company he founded says it is building a 14-acre campus that over 10 years time will have more than 2 million square feet of building space in the Mission Bay neighborhood of San Francisco.

According to the San Francisco Chronicle, Salesforce already occupies more than a half million square feet in an assortment of buildings downtown and South of Market, centered at The Landmark @ One Market. That makes it the largest technology company in the city by square footage, followed closely by Lucasfilm Ltd. and Dolby Laboratories Inc.

While we have chronicled some of the best cities around the globe for startups to set-up shop, the San Francisco area is still the promised land for Internet entrepreneurship. Others come close, but no other city can match the vibrant atmosphere that flourishes in the Bay Area, but what are the best neighborhoods for tapping into the startup ecosystem? Posterous co-founder Garry Tan has sought to solve this problem for San Francisco newcomers by creating an interactive Google map detailing the area's top 10 startup camps.

It's not every day you get the chance to hear a half dozen executives from successful startups speak openly about how their companies managed to get to where they are. In fact, its most likely that to get that kind of access in one day, you'd have to be at some high-priced convention that costs several hundred dollars to attend. This isn't the case, however, with Starter Day, an event hosted by software makers Atlassian that will showcase six CEOs and founders from various startups, including Boxee, Aardvark and Pandora.

We've all heard of the big company that started as two guys in their garage, but these days, with startup organizations and incubators, more and more success stories seem to feature companies that built their success from group collaboration. One excellent example of how startups can take advantage of collaboration is to work in a coworking environment with other companies and entrepreneurs.

Monday evening I was made aware of a particularly interesting promotion that will be taking place over the course of two days before South by Southwest (SXSW). The event, or tour, is called The Startup Bus, and will challenge 12 participants to create as many tech

In an effort to highlight some of the emerging tech centers across the world we've written on a number of cities for our Never Mind the Valley series. We've featured the funding and opportunities available in places like Washington DC, Bangalore and Beijing. Our intent has never been to create regional rivalries, but rather to highlight the diverse landscape of the tech world in general. That being said, few stories got as much attention as the piece on New York as passionate East Coasters rallied around their hometown. Despite what seems to be a surge of love for the Big Apple, SpeakerText CEO Matt Mireles recently pointed out the shortcomings of the New York tech scene and announced that he's exploring the Valley for opportunities.

The talk of the venture capital and entrepreneurial towns these days is the Open Angel Forum which after its second event in Boulder, Colorado is now announcing two more events in New York and San Francisco. Brainchild of Jason Calacanis, the Open Angel Forum (OAF) is an opportunity for startups to get face-time with active big-time venture capitalists and angel investors - all for the low, low price of free.

For once the Bay Area Rapid Transit service has more to brag about than its endless supply of used under-the-seat bubble gum and noxious mystery smells. According to its site, Bay Area Rapid Transit will be the first transit agency to partner with location-based game sensation Foursquare.