Bandcamp - Discover amazing music and directly support the artists who make it.
Gnoosic - Even if you don't know what you are looking for - gnod will find it.
SoundCloud - Enjoy music & follow favourite artists
Musicroamer - A visual Pandora for discovering new music
Pandora - Pandora Radio is a free (ad-supported) internet radio founded in 2000.
TasteDive - TasteDive recommends similar music (musicians, bands), movies, TV shows, books, authors and games, based on what you like.