Polygon definition and properties
Math Open Reference

Definition and properties of parallel lines
Math Open Reference

octagon
Math Open Reference

Definition and properties of a nonagon (enneagon)
Math Open Reference

Definition and properties of a hexagon
Math Open Reference

Definition and properties of a heptagon
Math Open Reference

Four different ways to test if polygons are congruent.
Math Open Reference

This is a great link to help find area, depending on whether you know the length of a side or the apothem. You can get a discussion of the various formulas and the page is also interactive which allows you to check and see if what you calculated is on target.
Math Open Reference

A site that allows to students to interact with various sized polygons and explore tesselations and symmetries.
Polygon Playground

Gives illustrations of the most basic and the most complex polyhedra
Cool Math 4 kids
