I searched Google a bit and did not find a trace of anyone doing a Flash implementation of Voronoi Diagrams. This is a pity as they do create some real nice patterns and they might even be useful for games or interfaces.
So what is this about? Imagine you have a set of dots on a plane. Now you draw borders between the dots in such a way that the enclosed areas contain all the points that are closest to the encircled dot. Well, if you want a better description read this
My first implementation uses the slowest of all thinkable algorithms, but I hope that I'll be able to speed that up. Just click a few times to add more dots, but beware it gets slow pretty fast. Download the source file here.