I picked this link up off of our news aggregator: Skating Robot. It is a pretty neat discussion of and some videos for a legged robot that can both walk and skate. Wheels at the tips of the legs can flip down and become feet. However, while in the rolling position there are no motors attached to the wheel. They 'free wheel'. The robot uses these like you would use skates.
I find the design to be quite original. At the very least I've never seen anything like it. As there description mentions, having the both the tradtional equipment for motorized wheels and the (seperate) equipment for motorized legs is cumbersome. The skating motion allows this robot to dispense with the wheel motorization equipment and effective replace it with the leg equipment via the legs skaing motion.
I'm interetested to try this out on my Bioloid stuff!