Pandora Internet Radio

A few years ago a group of musicians created "The Music Genome Project." This group categorized tens of thousands of songs into hundreds of sub-genres based on melody, harmony, rhythm, orchestration, arrangement, lyrics, and vocal harmony.

Out of this project came Pandora Internet Radio. Pandora automatically creates commercial-free radio stations based around bands that you like. You can rate the songs that play on the station (thumbs up or thumbs down) and Pandora will adjust the playlist accordingly. It's a great way to find new music.