Steve Gibson of grc.com and Security Now guided me to SpaceMonger - a disk / file visualization tool. Think in terms of size, age, and other file attributes - then map multiple variables of a hierarchy in a map with size and color to differentiate. The results are stunning visuals that let you immediately hone in on relevant criteria. Over the last few years similar maps of the stock market with industry and company information have become popular.
But now the best part! All of this technology is based on research conducted at the University of Maryland. Documentation and flash video tutorials are online and available!
Treemap is a space-constrained visualization of hierarchical structures. It is very effective in showing attributes of leaf nodes using size and color coding. Treemap enables users to compare nodes and sub-trees even at varying depth in the tree, and help them spot patterns and exceptions.
The research team has also developed tools (free for academic use) to create treemap. The current version is 4.1.1 and is available at http://www.cs.umd.edu/hcil/treemap/ .