Playlist Machinery - Tools that help you create & organize your Spotify playlists
last-slack - Display your scrobbled tracks from last.fm in Slack
Party Blends - A way to blend your friends favourite tracks into one Spotify playlist.
Owlead - Grow your Twitter with valuable followers, effortless
Ranked Records - Create Spotify playlists with all an artist's songs
Sound Control - App-specific volume control