Songstack - Swipe to discover new music for Spotify
mixmello - mixmello is a free, open source tool to create remixed versions of your favourite playlists.
remixmonsta - Tired of Despacito? Find a cool remix instead
Music Walker - Explore and play (via YouTube) songs similar to a seed song.
Remix - Solidity IDE (Integrated Development Environment)
stats.fm - With the click of a button you'll be logged with your Spotify account and you'll instantly gain access to a valhalla of cool stats and insights.