TreeMap.Net
MS Research has been working on an interesting thing: .NET components that display hierarchical data as a set of nested boxes.
For questions or comments, go to the microsoft.public.research.netscan.discussion newsgroup.
It seems that this tool was used first to do a newsgroups survey and analyze their importance in cyberspace.
The site C2i give an example on how to use TreeMap to show the space files are using on an hard drive.
Again amazing thing from MS Research.