Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Songstack - Swipe to discover new music for Spotify
BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
remixmonsta - Tired of Despacito? Find a cool remix instead
Musicroamer - A visual Pandora for discovering new music
The Rick Astley Remixer - Remix your favourite songs in your browser.