Q: What's a good module for making node diagrams?

[Robert Rothenberg]

I would like to make general node diagrams, such as of binary trees, linked
lists and skip lists.

I've tried UML::State, but it does not allow one to control the size of nodes
and may not be flexible enough to make trees.

I can't figure out SVG::Graph, if it is even capable of doing this (it looks
like it has hooks, but that's it).

Are there any other modules?