yeah, Pandora and the Music Genome Project are pretty cool. This isn't really like a "personalized radio station" though. It is a way to discover other music that is similar to the music that you already like. You won't hear the same artist more than three times in an hour because of the licensing deals they have. You also cannot request a specific song because of this.

They are adding stuff on a daily basis over there, and they have some interesting licensing deals with the RIAA/artist groups.