Magic Playlist - Get the playlist of your dreams based on a song
Heartbeat - Listen to music with your friends together, on Spotify
Spotalike - Spotify playlist with similar songs, according to Last.fm
Liyo - Stream your favorite music live with friends 🎶
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Parallel - Listen to music with friends over Spotify at the same time