From Music Hack Day
 About the Hack
Use a Bookmarklet to add songs to your "Play Later" queue, add them yourself, or have your friends collaborate on your queue. Then listen whenever you like. Your friends can also listen along while you take control. Uses Rdio API for playing, along with WebSockets, Ruby on Rails, CoffeeScript and all that trendy HTML5 jazz to make a live syncing and playing music interface for multiple parties.
 What APIs, tools or kit did you use?
Ruby on Rails, CoffeeScript, SASS