I use OmniGraffle as a mindmap software when I want to produce nice looking mind maps. Using the drawer with the outline function and automatic layout makes it as fast as a dedicated mindmap software to build the tree. Then a bit of manual re-arrangements are necessary to make it look like a "true" mindmap. The advantage is tahe the graphic capabilities are far better than the specific mindmap softwares, so based on a mindmap you can produce a better and richer graph. :)
Novamind is a mindmap software with some graphic capabilities. But if you look for the reference in terms of mindmapping, I believe Mindmanager is the one, in terms of functionalities, exchanges with other apps, Windows/ Mac, free viewer...
A free and easy mindmap software is freemind, works on Mac and Windows :)
http://freemind.sourceforge.net/wiki....php/Main_Page
I personnaly believe that OmniGraffle could become an excellent mindmap software if the layout engine was improved, as well as the conversion back and forth with OmniOutliner. I wrote about it to the OmniGuys a couple of times. if you feel the same... tell them! ;)
Cheers