What it is:
A cross up of social chat and music playlists. Typically different chatrooms cater to different music and users join a chat room where they can then take a shot at being one of the DJs for the room (space is limited in the popular chats) or just hang out and groove along.
The model for these websites seems to capitalize on hipster indie music type scenes and take advantage of streaming music over the Internet (like Pandora or Last.fm) and merge it with social media.
The aforementioned hipster indie social scene, but a good subset of techno lovers and especially dubstep aficionados.
Screen-caps: (Click the images for a larger version)
From the screen-grabs you can see that users in a room can rate the currently playing song (lame/awesome vs weak/hot respectively). There’s a window where you can queue up your DJ set list and another window for the chat component. The ever-present avatar for your special virtual self is populated within the room. Modifications can be made to your avatar and run the gamut from the basic level to higher level options. Positive song ratings add points/credits to a user which unlocks other appearance mods.
As far as music selection goes, both sites offer the same selection of popular music (available in the US currently due to licensing restrictions). However, the classical selection is middling to fair with a lot of tinny sort of midi-type tracks that annoy the crap out of me. I think the graphics for Turntable are much more slick and creative (using a wide range of skin tones and non-human avatars will always get points with me). Yet I am annoyed that I cannot preview all the songs on my playlist before I start playing them in a room [insert something about music licensing reasons here].
Gotta pick just one? I’m going to go with Turntable.fm for now. But, to be honest, I probably won’t log into the site all that often.