Got a spare Denso 6DOF industrial robot arm? Why not program it to play the integral role in a large round clock, hypnotically sweeping back and forth in regular, smooth arcs, plucking bricks and moving them, resetting them and keeping time? Seriously, this is endlessly fascinating. Link (Thanks, Dean!)
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.