Baloen GTK allows you to create, modify, save and load graphs from many popular formats. You can also simulate various famous graph algorithms such as for example hamiltonian cycle and breadth first search. But that's not all... For a showcase of the full possibilities, check out http://www.youtube.com/watch?v=O8FpRwV6X-M
This program was ported from a private SVN repo and hasn't been looked at since 2011. In order to run it you need Qt. Just open the .pro file, compile and run!
Balazs Nemeth ([email protected]) and Jeroen Vaelen ([email protected]). Feel free to contact us with your questions.