I would like to anounce my sign up to another profile type site. last.fm
last.fm captures your music history and recommends more music for you to listen to. It also has loads of other cool features (statistics) of your listening behavior. I have also put a little badge of my listening on the side bar. The social part is in how you can look at your friends listen habits, write reviews, create your own radio station based on your listening. Playlists (mixtape...), and other sharing of music love.
oh. and they have cool widgets...
(drawing by Kelly Vivanco (Patches))