Tempso - Finally a place for classical music online!
Gnoosic - Even if you don't know what you are looking for - gnod will find it.
musicForProgramming(); - Mixes intended for listening while programming
Musicroamer - A visual Pandora for discovering new music
Music-Map - The Music-Map is the Tourist Map of Music, part of Gnod, the Global Network of Discovery.
TasteDive - TasteDive recommends similar music (musicians, bands), movies, TV shows, books, authors and games, based on what you like.