Poolsuite™ - The super-summer music player
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Tiny Mix - NPR Tiny Desk — mixed up, one song at a time.
Playlistor - Convert Apple Music playlists to Spotify and vice versa
Magic Playlist - Get the playlist of your dreams based on a song
Tune My Music - Transfer Playlists Between Music Services