Here's all the demonic summoning symbols you're likely to use on a daily basis, in handy flashcard form. All you need to do is print it up and stick it over your monitor, so it's handy when you need it.
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.