Slackbox - Spotify playlist collaboration through Slack
BeatSense - Discover great music hand-picked by real people, in a single click. FREE and in real-time!
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Twinjack - Stream Spotify music with anyone with just a link
Exportify - Export your playlists from Spotify
Liyo - Stream your favorite music live with friends 🎶