Andy from the Royal Institution made a large, suspended Möbius strip out of rare-earth magnets, then cooled down an object until it became a superconductor, and set it levitating and running around the track. The result is amazing, plus Andy's explanation is cogent and fascinating. Plus, gravity-defying levitation!
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.