Geopaper is an experimental publication that allows for the construction of accurate regular and irregular polygons from triangles to icosagons.
It is great for an IWB and suitable for supporting a variety of geometry topics including exploring shape, perimeter, area, Pythagoras and trigonometry.
http://www.interaktiv.co.uk/izones/polygons/geopaper
Some example of geopaper in action:
An equilateral triangle with all lengths and angles shown.
http://www.interaktiv.co.uk/izones/polygons/1.png
A regular icosagon with just the lengths shown:
http://www.interaktiv.co.uk/izones/polygons/2.png
A Right angled triangle with two lengths shown
http://www.interaktiv.co.uk/izones/polygons/3.png
An irregular dodecagon with a mixture of lengths, angles and algebraic substitutes.
http://www.interaktiv.co.uk/izones/polygons/4.png
Mack