Theo Jansen builds amazing walking machines as can be seen in this video:
http://www.vimeo.com/1242383

Each leg is an eight-bar linkage. The Wolfram Demonstration Project models this linkage in a Mathematica notebook. See the link:

http://demonstrations.wolfram.com/ATheoJansenWalkingLinkage/

The National Institute of Standards and Technology provides an on-line periodic table. Access it and other information at the link:
http://physics.nist.gov/PhysRefData/PerTable/index.html

National Institute of Standards and Technology

This is a link to notes on Geometric Design and Tolerancing by Prof. Graeme Britton of Raffles Design Institute, Singapore:
http://www.docin.com/p-6099896.html

Prof. Britton's Notes on GD&T

A pdf version of Prof. Britton’s lecture is available at:
http://synthetica.eng.uci.edu/~mccarthy/mechanicaldesign101/GDandT.pdf