Musicroamer - A visual Pandora for discovering new music
Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Music Walker - Explore and play (via YouTube) songs similar to a seed song.
Songstack - Swipe to discover new music for Spotify
LivePlasma - Discovery engine map for books, music, and movies
mixmello - mixmello is a free, open source tool to create remixed versions of your favourite playlists.