well this is a site where you put the name of a band or a song and the site will create a playlist with songs and artists that has some relation with the one you wrote.
It also explains "why this song is being played" and you can tell it if the song it showed you you liked it or you didn't so the next song will be closer to your taste.
Each playlist has a top limit of 7 songs, and you can have 100 playlists, and you can mix all playlists. You can also add to one playlist you made more band or songs names so the results will be closer to what you are looking for.
Well, I recommend you this site, you will enjoy it a lot. It's kinda vicious, so go there; you won't be disappointed.

www.pandora.com

          > Iszil

This link has been posted before by someone, and my choice key-names were still in the menu!
But it is cool just the same!