SpaceSniffer
SpaceSniffer is a portable, freeware program that helps you understand the structure of the folders and files on your hard drives. The Treemap visualization layout SpaceSniffer uses helps you to immediately visualize where big folders and files are placed on your devices. The area of each rectangle is proportional to that file’s size. You can double-click on any item to see more detail: http://www.uderzo.it/main_products/space_sniffer/index.html.