Strange beautiful music

A friend of mine gave me this link: http://www.pandora.com. If I had to define it I would probably say: it's a customizable thematic web-jukebox. You just put the name of a musician you like and the system plays songs with the same "feel": great way to learn new songs! An example: the "led zeppelin radio" transmits led zeppelin (of course!), Jimi Hendrix (because of extensive vamping and heavy instrumental improvisation), free (because of electric guitar reefs and solos), Rory Gallagher (because of vocal-centric aesthetic), Nazareth, Judas Priest, … Ah, it's free.