When Iñigo Quílez isn't hard at work at Pixar, he's active in the demoscene, creating 4KB programs that render incredible procedurally generated scenes. He also writes tutorials on both video and audio synthesis, but arguably the coolest section of his site features live-coding videos of him improvising both audio and video rendering code that will make any experienced programmer feel wholly inadequate.
Geometry, Surfaces, Curves, Polyhedra (many of which are beautiful) l Google Earth Fractals l fractals and chaos. [more inside]
It's not a bug, it's a feature: Carolin Horn has designed Anymails, which represents your email messages and folders as micro-organisms. The morphology of the individual organisms and their behaviour within colonies imparts information about the state of your email. You can view QT movies of the application in action (1, 2), download her thesis, and download the Anymails code itself. See some of her other work here (predominantly in German). via Madame Martin, the "French Metafilter".
Magic Ink - Information Software and the Graphical Interface