FreeMind is a mind mapping tool developed with the intent of being fast and flexible. FreeMind can run Mac OS X, Windows, and Linux. It is available for free download from the FreeMind website: http://freemind.sourceforge.net and is licensed under the GNU General Public License. FreeMind is also opensource, which means the materials used for developing FreeMind are available to anyone. This allows anyone to develop FreeMind, or use the materials for other projects.
Here is an example of a mind map made in FreeMind:
The items that hold information and connect to other items are called nodes. Using nodes in FreeMind is easy: To edit the content of a node, click on the node and start typing. To add a child node (ie. sub node) use tab on a Mac or insert on a PC. Then begin typing in that node. To add a sibling node press enter.
That covers the majority of what is involved in using FreeMind. For further information visit http://freemind.sourceforge.net/wiki/index.php/Documentation or click on documentation under the help menu in FreeMind.