Party Play - Introducing Party Play. One playlist for multiple users.
Magic Playlist - Get the playlist of your dreams based on a song
MisterJack - Make and share playlists
Spotalike - Spotify playlist with similar songs, according to Last.fm
Festify - Festify is a free Spotify-powered app that lets your guests choose which music should be played...
Playlist Machinery - Tools that help you create & organize your Spotify playlists