All you music lovers, check out Pandora.
It is a Music Genome Project. A group of musicians and music-loving technologists got together in early 2000 and began the process of deconstructing songs. They paid no attention to the category the music was assigned or the look of the band -- only the structure and musical qualities of the songs. (Who has time to do things like this?)
Therefore, you choose an artist or a song you like and Pandora chooses other songs that should be complementary to those typical of the artist you've chosen or those most like the song you've chosen. I've tried it and, for the most part, it does a good job. Check it out.