Spotube
Open source Spotify client that doesn't require Premium nor uses Electron! Available for both desktop & mobile!
Spotifyexplore Musicsongnames
Connecting Spotify songs to MusicBrainz to find new music based on song titles
Playlastify
A webapp visualizing your Spotify playlist stats with Spotify WebAPI & Last.fm API
Lyricy
A command line lyrics utility tool which search and add lyrics to your offline songs.