ReadWriteWeb

Denver, Colorado based Superhero.es has built crgslst, a very slick multi-city search tool for Craigslist. Craigslist itself doesn't offer a multi-search service. By combining the publicly available RSS feeds from Craigslist with AJAX, crgslst fills this need "so fast, we left the vowels behind."

Unfortunately, crgslst may be in violation of the Craigslist terms of use and could face the same shutdown that other similar projects have in the past. This situation brings up a number of questions about intellectual property, RSS and mashups.

Songbird, the little music player/web browser mashup that everyone has high hopes for, has just released a new version: 0.5RC1. This is their first official release towards their goal of having 0.5 Final out later this month. This latest version offers some new features and improvements over version 0.4, including MTP Device Support for Windows users, a new Device API, and a new feature called "Media Views."

Twitter was originally designed as an app that would allow people to share information about what they were doing within a distributed group setting. It's something akin to a collection of automatically forming email discussion lists (except not via email). The benefit of this is that people can receive and send information within a group very quickly. That's why Twitter has become such an important source of breaking news, and it's also why helpful consumer information apps like Commuter Feed are possible.

Last.fm is generally acknowledged to be one of the best web apps of this era - its music recommendation system literally creates a personalized radio station for you. But the now CBS-owned service doesn't get nearly enough credit for its API. We've heard stories about how 90% of Twitter's use comes from its API. Well, Last.fm also has an API that is used by many external services to add value for end users.

In this post we list 10 of our favorites, but there are many more of them to explore. We invite you to add your favorites in the comments, along with a note about why you like them.

There's an old well-worn addage that says, "The customer is always right." On the surface, it means that you should always strive to provide good customer service. But on a deeper level, it means that if your customers do things with your service that you never intended, perhaps you should just go with it. That's likely what happened with Twitter, which started out as a place to report the random little happenings in your life, and has begun to evolve into a platform for serious discussion and breaking news.

Chicago based MoveSmart.org is a project aiming to make housing integration a reality, years after legal changes have left de facto segregation intact, by using mashups. The project will combine collections of data concerning public amenities and services, demographic data and economic numbers together with housing search.

Think of it as Trulia plus, with a social justice angle, or Zillow for people interested in more than just the price of a house.