Wolfram Research
Wolfram Science World: Elasticity
Over 30 equations which define quantities which server as measurable parameters of an object's elasticity are given. Some equations are derived and the derivations are explained. Highly technical!
Johns Hopkins University
Johns Hopkins University: Properties of Solids
From the General Physics for Bio-Science Majors web site. Several properties of solids, many of which pertain to the elasticity of materials. Stress and strain are defined and Young's modulus is explained. The Young's modulus equation is...