Basic mechanics of soils

Explains analysis of stress and strain, strength, etc in soils with good visual diagrams: http://environment.uwe.ac.uk/geocal/SoilMech/basic/soilbasi.htm

Dams

An interactive site that explains how dams crack and the forces that interact with dams http://simscience.org/cracks/index.html

Mohr Circle construction

Shows mohr circles for common stress states, how to, etc.

http://www.tech.plym.ac.uk/sme/mfrg315/mohrc1.htm

 http://www.ijee.dit.ie/OnlinePapers/Interactive/Philpot/mohr_learning_tool.htm

Fantastic website that covers all aspects of the all important Mohr's circle. Has interactive tutorial style questions and great  explanations and visual representations. Highly recomended

http://www.doitpoms.ac.uk/tlplib/metal-forming-1/printall.php

Mohr's circle explained in much depth.