Boston Dynamics is building this four-legged robot for the U.S. military (DARPA):
A nimble, four-legged robot is so surefooted it can recover its balance even after being given a hefty kick. The machine, which moves like a cross between a goat and a pantomime horse, is being developed as a robotic pack mule for the US military.In this amusing or perhaps creepy video (28MB Windows media file), the robot walks over different types of terrain--including mud, rocky ground, and snow--and is given a few kicks to show how it stabilizes itself. Unlike the photo at left, in the video it looks like a pantomime horse with both people facing each other--sort of the opposite of a pushmipullyu.
(Via jwz's blog.)