Secret Storage Books sells old hardcovers (mostly remainders and what look like library discards), professionally hollowed out and glued together to form hollow book stashes. You can choose the book that will look most convincing on your shelf. Most of the titles run less than $35. Link (via Schneier)
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.