Video Riot Lets Users Create Their Own YouTube Mashups
Video Riot by artist Scott Draves is a site that lets users create psychedelic mashups of any YouTube video thanks to the magic of WebGL (currently enabled on Chrome and Firefox). For example: crazy time acid trip Keyboard Cat.
The effect is based on video feedback implemented with WebGL and its shading language, which means most of the work is done on your GPU. The videos are in WebM format which works on Chrome and Firefox.