aux.app - A free web-based music platform to play music from other popular online streaming services.
Magic Playlist - Get the playlist of your dreams based on a song
Jukebox - Collaborative music player
Spotalike - Spotify playlist with similar songs, according to Last.fm
CueBot - A better way to request for songs at a party 🎉
Playlist Machinery - Tools that help you create & organize your Spotify playlists