Momixa - Pick two songs and get the perfect mix
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Music Suggestions Ninja - Enter an artist's name & find similar, lesser known artists
Playlistor - Convert Apple Music playlists to Spotify and vice versa
Boil the Frog - Create a seamless playlist between any two artists
playAppleMusic.com - An (unofficial) web player for Apple Music