You can discover new music on a lot of different services, but Turntable.fm is a bit less formulaic. Instead of picking your music for you, you can create playlists with other similar-minded folks and listen to them in real time.When you start up Turntable, you can create your own "room" or find one that's playing music you like. Once you enter a room, you'll see a number of cartoony avatars hanging out, with a few at the top DJing. Turntable cycles through each DJ one by one, each playing one song at a time. You can "like" or "dislike" songs as they play, and "liking" a song makes your avatar do this distractingly awesome head bob. If enough people dislike a song, Turntable will skip it and move on to the next DJ. You can also DJ yourself if there's room, and add songs to your queue through Turntable's database (or upload your own tracks).
It looks silly, but is actually pretty fun. You can chat with other users as you listen to similar music, and it's a pretty good way to find music you like from other people rather than a "formula".
It is a mad productivity killer, though—team Lifehacker got very little writing done in the hour we spent on Turntable—so make sure you don't try this at work. Seriously, you might think you'll just "leave it on in the background", but you underestimate how fun it is to make your character's head bob up and down. No, really.
Turntable's currently in beta, so you need a Facebook friend that's already on Turntable to get in. If you do, though, logging in is a one-click process, which is pretty convenient. Hit the link to check it out, and watch the video above to see it in action.