Playlist Hunt - Playlist Hunt is one of the best applications for Apple users to get the best music through it.
Magic Playlist - Get the playlist of your dreams based on a song
Book Playlist - Collaborative music playlists for your favorite books
Spotalike - Spotify playlist with similar songs, according to Last.fm
Musicon - An interactive music-making machine for children
Playlist Machinery - Tools that help you create & organize your Spotify playlists