- A graph datastructure that provides callbacks for node insertion or modification and import functions for the graphviz  dot graph description language.
- A dynamic layouter that can be bound to a graph datastructure via callbacks/events. It provides raw graph layout facilities and can be bound via callbacks/events to a graph display, for example the Tk canvas.
schlenk: It should be possible to use tclgdl to easily layout a graph created with ::struct::graph. One would have to implement some callbacks, so tclgdl gets notified about insertions and modifications on the graph, and one had to provide a basic rendering infrastructure to show the graph on a canvas.
EMJ (01 Sep 2011) : No link here except http://www.graphviz.org, doesn't seem to exist there, or anywhere else.