Voronoi Treemaps (Caution: 19 MB file) came to my attention by way of Jack Park.
A Treemap is a visualization of hierarchical data that uses squares to represent nodes in a tree. The size of a square depends upon a value assigned to it, based on some range of measurement. One drawback of this method is that complex or deep hierarchies are difficult to render for effective use.
The authors provide an excellent introduction to Treemaps, the current state of their use, as well as providing a method that allows the use of Treemaps visualizations with arbitrary shapes.
Computationally complex, Voronoi Treemaps may not be appropriate for real-time renderings of topic maps or domains for mapping.
The visualization of data domains as an aid to the creation of topic maps should include Voronoi Treemaps as part of its research agenda.