I have written before about mind-mapping software, and I heartily endorsed FreePlane as an Open Source tool that was light and easy to use. And it still is.
But just today, while researching LMS's I came across this little nugget:
it's another mind-mapping tool, but this one is based on the eclipse IDE platform. It's a heavier download/install, but the d/l package immediately includes the mac, windows & linux variants, and they are self-contained, so there's nothing more to installing them than to drag the appropriate app folder somewhere sensible, double-click on the application, and voila! it opens.
The app itself is running very smoothly, allows drag-and-drop re-ordering of your mind map/tree, and has several built-in themes (almost all usable!), and several dozen pleasing graphics to spice up your nodes.