Pandora is an automated music recommendation and Internet radio service created by the Music Genome Project. Users enter a song or artist that they enjoy, and the service responds by playing selections that are musically similar. Users provide feedback on the individual song choices — approval or disapproval — which Pandora takes into account for future selections.
So, basically you register and create different "stations" that will play music related to songs and/or artists that you select for that station. I love it because it introduces you to new music that you've never even heard of but will most likely like. And if you don't, you just tell it so.
I'm addicted and already have five (diverse) stations that I rotate depending on my mood:
- Indescribable Funky Fun
- Piano Rock
- Pop (Relaxing)
Also, you can share your stations with friends and listen to each others'. Basically, it rocks and it doesn't cost you anything!