Jeff Moser's "A Stick Figure Guide to the Advanced Encryption Standard (AES)" beautifully presents the history, context, and workings of one of the most important pieces of math in the modern world. AES is at the core of virtually every privacy technology you use, and it holds the promise of building an NSA-proof, unsnoopable Internet.
(via O'Reilly Radar)
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.