Cut the Knot
Cut the Knot!: Napoleon's Theorem
Site that describes in detail Napoleon's theorem. To understand this site be sure you understand what the centroid of an object is. The site describes polygons in terms of the roots of unity of a function. The page gives an interactive...
Jim Loy
Jim Loy: Roots of Unity
Contains relevant information regarding to roots of unity and a few examples, including diagrams. Information is helpful and concise.