YouTube's TheInternetFTW shows off this arithmetic logic unit (ALU) that he's built out of blocks and chunks in the game Minecraft. It's part of a larger "Hack" computer (as described in Elements of Computing Systems).
So basically, this is a computer subcomponent that you can run around on, physically moving around and watching as it does its thing. It's the 21st century equivalent of the wonderful Bell Labs Cardiac Computer that I played with as a child -- a cardboard computer that got me interested in computing when I was six or seven. It is the virtual made visceral, an unpacked microscopic mystery. It is sheer genius, better than any ten boring lectures on ALUs, computing theory, Boolean math, etc. It's the kind of thing that makes me wish I was a kid today, and glad that I have a kid of my own.
16-bit ALU in minecraft (Thanks, Fipi Lele!)
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.