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
Music-Map - The Music-Map is the Tourist Map of Music, part of Gnod, the Global Network of Discovery.
LivePlasma - Discovery engine map for books, music, and movies
Poly-graph Hip Hop - See what hip hop's billboard top 10 sounded like