Yet another primitive noise type has joined my library: Worley noise. This type of noise is directly based off of the concept of Voronoi diagrams. A Worley noise algorithm simply distributes a set of random points in 2-dimensional space and then computes the distance to the nearest point at a given pixel. The distance computed determines the color value of the pixel.
Interestingly, Worley noise resembles heavily-eroded perlin noise to some degree. It produces fairly convincing heightmaps with characteristic sharp slopes.