MindNode is a free mindmapping tool.
Elegant, with bright colors and light interface.
Easy to use with fast keyboard navigation.
It's very good for what it does: write your ideas, organize your thoughts and thoroughly explore the topics you study.
It's really a "tool" with a simple goal: it presents your ideas in a nice way, but some features are missing: personalize rtf exported data, for example.
It's free, and therefore a very great software: can't beat the price, can you?
But Freemind is better for its features. However, its defaults are Mindnode's qualities: stability, speed and look-and-feel.
Free-Node would be great, then!