Turntable is a musical chat room. You like talking to your friends. You like playing your favorite songs. You like hearing good songs you didn't pick. Turntable puts all of these nice things into one cartoonish online dance floor. Five DJs at a time queue up tracks of their choosing, while everyone else sits back and enjoys. Or doesn't enjoy! If a dud comes on, the audience can vote it off the speakers with enough dislike clicks. Or if a DJ's playing good stuff, you can reward them with likes, which translate into points, which are worn around as a badge of distinguished taste.
http://turntable.fm/ <- the actual website
Says invite only but if you have a facebook you're good to go, i believe. Try it out if you can.