Tcldot is the Tcl package for Graphviz: the Graph Visualization Software. It makes the dot graph renderer available to Tcl scripts. See http://www.graphviz.org/cgi-bin/man?tcldot for the documentation.
Graphviz is available for Windows, Unix and MacOS X.
For an example, see XML Graph to canvas
schlenk If you need Tcldot for Windows, send me an email, i might find the dll and the VC6 project file.