The strandbeest is a walking machine developed by Theo Jansen. Its cleverly designed legs consist of single-degree-of-freedom linkage mechanisms, actuated by the turning of a wind-powered crankshaft.
His working models are generally large - something of the order of the size of a bus. Look for videos on YouTube. Commercially made small toy models are also available. This one sells for under $10 and it's fun to assemble and works quite well. Beware that the kit consists of over 100 tiny pieces - so assembling it is not for the impatient type.
Here is a Maple worksheet that produces an animated strandbeest. Link lengths are taken from Theo Jansen's video (go to his site above and click on Explains) where he explains that he calculated the optimal link lengths by applying a genetic algorithm.
Here is a Maple animation of a single leg. The yellow disk represents the crankshaft.
And here are two legs working in tandem:
Here is the complete beest, running on six legs. The crankshaft turns at a constant angular velocity.
The toy model noted above runs on twelve legs for greater stability.
Download the worksheet: strandbeest.mw