There is a few websites about structural geology that I visit once a week or more often. I would like to start a series of articles for briefly presenting them.
The first of this sites is "Structural Geology Techniques", in charge of Steven Dutch, professor of the University of Wisconsin. (http://www.uwgb.edu/dutchs/structge/labman.htm).
In the website of Dutch, a neat and organised page, you can find many examples and diagrams explaining a good range of geometric problems related with structural geology. There are from basic level problems (e.g., calculatina fold axis given the limbs of the structure) to not so fundamental problems (e.g., how to construct a down-plunge cross section).
As Dutch explaines in his homepage (http://www.uwgb.edu/dutchs/index.html), he does not like fancy graphics, and his website is an example of efficient diagrams, which isn't always the same as beautiful. However, they are clear and functional.
Visit the place if you didn't know it yet. You will be surprise with how many things you have forgotten of structural geology and geometry :-).