A Voronoi diagram is created from a set of points by dividing the plane into regions, where each region consists of the area closest to one of the points. Ken Shirriff published a paper about voronoi fractals ten years ago. Frederik Van Houtte from Belgium created a nice applet with the processing language to generate online voronoi fractals.
Click the applet to generate a new fractal.
A description of the project and the source code are published on Frederiks weblog under a a Creative Commons license.