I ran across this nice animation on creating a pentagon from a circle (taken from Wikipedia):
I thought this would make a great Math Forum project, and I just posted it as this month's free project.
It's a neat exercise in 2D thought: starting with one common object, a circle, and without knowing any numbers or angles, creating all the necessary lines to make a pentagon.
The Student Version has a question at the end about the number of circle segments you need to use for this project. The Teacher Version has the answer.
Anyone can design anything in 3D! http://www.3dvinci.net/