Electric Sheep is a distributed computing project that calculates beautiful, fractal-based animations that self-modify based on users' feedback, evolving into gorgeous artificial life-forms. Link (Thanks, Steven!)
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.