Grooveshark is more of an online jukebox than a radio station - no restrictions on how you choose to play music, no audio ads, totally free. Its music finding algorithms aren't on a par with Spotify or Pandora (goodnight, sweet prince), but they've massively improved their social functions as of late; I now discover the majority of my new music by following friends with variously diverging tastes to me.

Should you choose to give it a try, I'm dbsurfeit over there - and very happy to share.