Update 2006.10.26 22:50 EDT: Just figured out how to capture the graph.
This is just one of those cool, nearly useless toys on the Web. The graphs it constructs are interesting in themselves, even somewhat informative, once you get used to reading them. It's fairly deterministic; if the Web page content is the same, you'll get the same graph. You can see lots of examples on Flickr.
I've done this a couple of times against my blog's home page, and it really does change as my blog's contents change. With a little work, you can figure out where the different structures come from. A blog entry with lots of photos is an outer ring of purple dots for the images with an inner ring of blue dots for the links. It looks like a dandelion head gone to seed.
But the really fun part is watching the graph get constructed. It looks alive - like a plant emerging, leaves coming out and unfurling, flowers blooming - as the applet parses the HTML elements. Then it slowly ... heals itself. It re-arranges its nodes to correct crossed lines, evenly disperse the nodes and "flowers" on the branches.
You can view the Flatbush Gardener graph. Since it's a Java applet, it requires Java to be enabled in your browser. It won't work from behind most corporate firewalls, I would bet. A high-powered graphics system is also strongly recommended!