Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Concertmaster - Classical music front-end for Spotify
Musicroamer - A visual Pandora for discovering new music
Tempso - Finally a place for classical music online!
TasteDive - TasteDive recommends similar music (musicians, bands), movies, TV shows, books, authors and games, based on what you like.
Classical - A classical music interface for Apple Music