I heard about GraphViz ( http://www.graphviz.org ) via an interview with the author of InstaViz ( http://instaviz.com ) and spent a little time this morning learning about how GraphViz works and how to use it.
If you haven’t already, check it out (and if you have a Mac, check out the award-winning OSX version at http://www.pixelglow.com ). When you’re freed from the need to think about layout, alot of potential applications for charts like this open up, and in my case this tool could play a significant role in a Google Wave (http:// wave.google.com) project I have been noodling on.