http://brasstacks.mozilla.com/toolbox/

You have a network of tools each with a set of fields (usage, author,
type, and language) each with an ordered set of values. The set of the
tools and field values represent the nodes of the graph.  The field
names are the values of the edges.

= Display =

The node size should be proportional to the number of edges connected
to it and with gravity also proportional.