The Music Genome Project

This is one of the coolest websites I've seen in awhile. You create a radio station based on a favourite song or artist. They will then play similar sounding songs. You then train the radio station by telling it if you like the song or not. I haven't been using it for too long, but I assume that eventually you would have a radio station that plays songs that you like all the time.

check it out: www.pandora.com