Magic Playlist - Get the playlist of your dreams based on a song
Replayify - Create playlists from your most played Spotify tracks
Spotalike - Spotify playlist with similar songs, according to Last.fm
CoverSutra - CoverSutra gives you a handy and attractive way to control iTunes without ever leaving your current...
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Jott - Fast, local, linked notes