A good diagramming software that is realtive inexpensive is Inspiration. http://www.inspiration.com It is available on both Macintosh and Windows systems. NovaMind Mind Mapping 3.2.0 for both platforms is also good. http://www.nova-mind.com/ ConceptDraw MindMap for MacOS 4.5 http://www.csodessa.com/ is also very good and easy to use.