You've seen BigDog, you've seen LittleDog. Now Boston Dynamics has invented the world's fastest robot, Robo-Cheetah. Capable of running at almost 30kph (on a treadmill, tethered, for now) it arches it's back to run more like an animal. There's a Wired article with a movie showing the headless beast at full stride. Boston Dynamics' YouTube channel has movies of their other projects such as the bipedal PETMAN and a six-legged climbing robot called RISE.