Here is a walking machine called the Mondo Spider:

The leg of this walking machine is described in US Patent 6,260,862 awarded to Joseph Klann. Access it through the link:
http://www.google.com/patents/about?id=70YHAAAAEBAJ&dq=6,260,862

Wikipedia calls this the Klann linkage described here:
http://en.wikipedia.org/wiki/Klann_Linkage

The leg of the mondo spider has the topology known as a Stephenson six-bar.