Today's XKCD is epic in scope -- a log-scale map of the observable universe from top to bottom, with many in-jokes (including me!) and pop culture references. How many can you decode? Height (Thanks to everyone who suggested this!)
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.