treemaps

Visualizing Data
Ben Fry

ref.    GoogleBook

Chapter 7: Trees, Hierarchies, and Recursion

treemap: Ben Shneiderman   http://www.cs.umd.edu/hcil/treemap-history/
map of the market: Martin Wattenberg   http://www.smartmoney.com/map-of-the-market/
newsmap: Marcos Weskkamp    http://www.marumushi.com/apps/newsmap/

an open source library for creating treemap structures (HCIL)
http://www.cs.umd.edu/hcil/treemap-history/Treemaps-Java-Algorithms.zip

a modified version as a Processing library
http://benfry.com/writing/treemap/library.zip
http://benfry.com/writing/treemap/equator.txt