Graph layout rectangle nodes

[King]

I am looking a way to layout my nodes. The application screenshot is
here:
http://pantheon-studios.in/shaderbox/

As you can see, nodes are rectangles. They have a position and size
(width is same, height vary). I need to arrange
them neatly. The easiest way I can describe the solution is.

1. Create a list of all nodes in the graph.
2. Store their position and size.
3. Create a list of edges.
4. Pass above information to a function.
5. Get back new positions of the nodes.

So we something in pygraphviz that can help me out here?

Prashant
Python 2.6.2
XP 32