Thank you for the suggestion. In return, I wanted to pass on one of my own. Cmaps is a free mind mapping tool. Though it is not as powerful as the ones mentioned thus far, it does allow one to make a stronger emphasis on the propositions connecting two key terms. It can run on all the major platforms and seems to be widely used around the world. Its link can be found at: http://cmap.ihmc.us/.
Has anyone had the opportunity to use brainstorm and mindola? I would be interested to see how that has worked out for other people.