Originally pioneered by Tony Buzan, a Mind Map is a type of diagram that is a radial organization of an outline. Mind Mapping is taught in prestigious schools such as MIT.
I like mind mapping. I have always believed that diagrams are the instrument of thought and the mind map is a great diagram for composers of all types or simply for those wishing to organize their ideas.
Here is my short list of open source mind mapping tools that are thriving in 2010.
Labyrinth is a Gnome tool so it is for Linux users only. Labyrinth can be easily installed from the Ubuntu software center. It's not the best tool by far but I end up using it because mind maps created in Labyrinth can be indexed by the search tool Beagle. Here is a screen shot of a labyrinth mind map of this very blog.
Freemind is a great stand-alone tool for mind mapping. The GUI doesn't get in the way of your creativity. Freemind is written in Java so it can be run from Windows, Mac OS X, or Linux. Files saved in one OS can be opened in another.
Semantik is written on top of KDE so it is another Linux only tool. It's focus is to aid students in generating documents based on mind maps. Semantik can also be easily installed from the Ubuntu software center.
You don't install Mind Meister on your local machine because it is a web application that you access through your browser. Mind Meister stays true to the original concepts of mind mapping yet extends those ideas in useful and relevant ways. Mind Meister is a commercial company based on the freemium model so you don't get to fully access all the features without paying a monthly subscription.
At first glance, Bubblus diagrams don't look all that much traditional mind maps. Like Mind Meister, Bubblus is also a web application that you do not install on your local machine. Unlike Mind Meister, Bubblus is free forever so you get full access to all of its features without a monthly subscription fee.
Mind mapping is a great way to explore the hierarchy of ideas through creative diagramming. These five free tools present the state of computer based mind mapping in 2010.