Graphopt is a graph layout tool that was created by Michael Schmuhl for graphs that other layout tools (Graphviz, for example) could not produce meaningful visual representations.
The current package version available from Sourceforge is from 2003, and depends on GTK+ 1.2. Some modern Unix/Linux distributions, for example, Debian sid, do not include GTK+ 1.2 libraries any more, and Graphopt was unable to be compiled under GTK+ 2.x.
I have updated the code to successfully compile under GTK+ 2.x, and have been working on a number of tweaks to the layout engine to optimise layout for certain classes of graphs.
As I have not been able to find contact information for the previous author, I am publishing the GTK2 version of Graphopt here.
The following plot has been generated from a set of 5900 edges, and 4000 nodes representing follower data on Twitter. Using Graphviz for this and similar data sets resulted in either faulty output, or a lengthy generation process.
Graphopt provides two import file formats: a limited parser for Graphviz's "dot" file format, and its own XML-like file format.
For export functionality, Graphopt provides an export to its own XML-like file format, and a Postscript output. An output to earlier versions of Visio is also included, but Microsoft has discontinued import support for this file format.
If you have any comments or queries, email me at graphopt at this.domain.org.
Graphopt has been released under the GNU Public License (GPL).