From Wikipedia:

Last.fm is a UK-based Internet radio and music community website, founded in 2002. It claims over 21 million active users based in more than 200 countries.
Using a music recommendation system called 'Audioscrobbler', Last.fm builds a detailed profile of each user's musical taste by recording details of all the songs the user listens to, either on the streamed radio stations or on the user's computer or some portable music devices. This information is transferred to Last.fm's database ('scrobbled') via a plugin installed into Jinzora. The profile data is then displayed on the user's profile page. The site offers numerous social networking features and can recommend and play artists similar to the user's favourites.

Use Jinzora to automatically submit every track you play to Last.fm to update your profile.

Community member Pirocho maintains a Jinzora Group over at Last.fm that you can subscribe to in order to meat people with similar interests.