I want to make an online application that does this (CLICK) only with more "nodes" then the examples four. However that example runs slow in IE7, so I'm ruling out using &#106avascript (what it uses) for vector graphics. I need a fast way to render network graphs with the ability to drag and drop nodes around. If anyone ever tried Yahoo! Pipes, that's what I want to do. Yahoo ! Pipes does use &#106avascript and its rather fast too. Whats the best way to render network graph data in a dynamic way? Flash? Java? Silverlight?

For LucidChart (see Instant Demo in my sig), I use &#106avascript and canvas (with excanvas for IE). Its performance is okay, but I've had to do silly amounts of optimization to get it to work well. If you're not worried about people who can't install plugins for one reason or another, I'd recommend doing it in Silverlight.

I was gonna suggest AGG until I realized you were looking to do this on the web.