You should check out Pandora. It's a site that lets you build your own "stations" around a given genre, artist, song, etc. For instance, you could start a new station with that song or artist, and it will find similar music to play for you. On top of that, for any specific song that it is playing, you can give it a thumbs up or a thumbs down, indicating you like or dislike the song. It basically learns what you like and plays it for you.

www.pandora.com