I should say I'm looking for something interactive, equivalent to what Nevron offers in it's .NET Diagram product, where a user can create nodes, interact with them by dragging them around, etc. I know there's GraphViz, but as far as I know it's static, and just renders a graph/diagram, there is no interaction with it.
I have a bad feeling there is nothing as rich as this in the cross platform world for Python or any other script language, but maybe I've missed it.