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
SonicRoad - Discover great music faster than ever before
playAppleMusic.com - An (unofficial) web player for Apple Music
FreeYourMusic - Migrate from and to any music services