Magic Playlist - Get the playlist of your dreams based on a song
vdNote - Share noteworthy moments from YouTube videos.
Spotalike - Spotify playlist with similar songs, according to Last.fm
YouDict - YouTube dictionary to search words, expressions & names
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Summary Panda - Remove annoying 'blah blah blah' parts of YouTube videos.