A web app that extends the capabilities of Spotify. You can create artists' discographies (all albums in a single playlist), merge multiple playlists into a new one with the ability to watch those playlists for new tracks, track live events for artists you follow or artists from a playlist.
I have been working on it for about a year now. It is not yet public because I am yet to apply for Spotify API quota extension, but I'd be happy to allow access manually if anyone wanted to take a look.