There is a website last.fm
. For some time he was completely free. It was possible to listen to music, make playlists and listen to playlists of other users (on their own player, good by the way).
But the main advantage of the site was the possibility of listening to music that was "close" to the user's taste and which he doesn't have in the playlist. That is, if you have in the playlist was the Enigma, the system you suggested (build a playlist "to taste") song Gregorian.
Now the service has to be paid. Does anyone has the same automatic social system of selecting the music according to the taste as last.fm
, but also free?