The KittenAuth test puts up a mosaic of cute baby animals and asks challenges the user to click on the kittens. This is easy for sighted people, pretty hard for software, and a little too incongruous to be a likely candidate for porn-based CAPTCHA solving. Ingenious!
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.