Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Songstack - Swipe to discover new music for Spotify
Musicroamer - A visual Pandora for discovering new music
22tracks - DJ curated Spotify playlists on iOS
LivePlasma - Discovery engine map for books, music, and movies
8tracks 3.0 (iOS) - Refreshingly human music playlists