Spotify.me - Beautiful analytics on your Spotify listening habits 🎧
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Magic Playlist - Get the playlist of your dreams based on a song
Playlistor - Convert Apple Music playlists to Spotify and vice versa
SpotMenu - Spotify and iTunes in your macOS menu bar
playAppleMusic.com - An (unofficial) web player for Apple Music