The concept sounds interesting. Now I just need to get a decent enough internet connection.
The basic idea is simple; create a profile, choose three artists you like, then the system picks and plays tracks based around not only the artists you've chosen, but also similar artists based on the preferences of others with similar tastes. It's an enthralling concept and one I'm a little disappointed I'm not able to really get into at the moment. If anyone is using Last FM I'd be interested in hearing comments.
Last.FM - Personalised online radio station