Scratch - Scratch is the programming language & online community where young people create stories, games, & animations.
Magic Playlist - Get the playlist of your dreams based on a song
Cyberix3D - Free online 3D Game Maker. Make your own 3D games online!
Spotalike - Spotify playlist with similar songs, according to Last.fm
Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
Spotify - Map shows when two people play same song at same time