Playlist Machinery - Tools that help you create & organize your Spotify playlists
Plug - Lightweight OSX player for Hype Machine
Spotify.me - Beautiful analytics on your Spotify listening habits 🎧
Magic Playlist - Get the playlist of your dreams based on a song
Playlist Hunt - Playlist Hunt is one of the best applications for Apple users to get the best music through it.
Spotify - Map shows when two people play same song at same time