Pandora - A neat music site

PANDORA:
Ever since we started the Music Genome Project, our friends would ask:
Can you help me discover more music that I'll like?
Those questions often evolved into great conversations. Each friend told us their favorite artists and songs, explored the music we suggested, gave us feedback, and we in turn made new suggestions. Everybody started joking that we were now their personal DJs.
We created Pandora so that we can have that same kind of conversation with you.

http://www.pandora.com/