I recently came across Constellation Roamer by Asterisq, written by Daniel Mclaren. It’s a very interesting flash-based tool for visualizing connected graphs within a browser. There’s a demo here if you’re interested in checking it out yourself.
I’ve not used it in any real world tests so far, but from my exploration it seems pretty good for getting a visualization up and running. It doesn’t compare with the hard-core scientific graph layout packages obviously, and it probably won’t scale to thousands of connections, but as long as you keep the data sets limited it performs well. There doesn’t seem to be much customization possible, the focus is on simplicity, and I couldn’t find any reference documentation. For example I couldn’t see a way to alter individual edge weights, or tweak the overall simulation parameters like friction and time-steps. That means I can’t use it for the massive simulations of Outlook Graph, but I am able to display a small social network painlessly.
The Asterisq site was a bit vague on the total cost for a single site license, so I had to go through most of the purchase steps to find out the $550 total. All-in-all could be a real time-saver if you want to build a small graph visualization into your site.