A graphical representation of how individuals visualize data connections. A fine example of the visualizer can be found here TouchGraphLinkBrowser.
Mind maps are often used in BrainStorming.
A mind map can also be used when you need to give a talk or presentation. Core concepts in the center, details on the outside. This allows you to "prune" unnecessary detail when you run out of time our your audience is not interested in a particular branch. This is an important advantage over documents structured as ordinary outlines and TableOfContents. Ideally, a hypertext can not only be represented as a graph (nodes/pages, connections/links), because such a graph fails to take relevance and memorability into account. Eg. in order to create a mind map based on a collection of wiki pages, you need additional information: A center to start from, major headings, some mnemonics, little pictures, cross references.
But how do you Mindmap? - A mindmap tool can help. There is FreeMind?, a free Open-Source mindmapping program, which can be found here: http://freemind.sourceforge.net . The site also lists other Mindmapping-programs. There is a wiki dedicated to FreeMind? and mindmapping here: http://freemind.sourceforge.net/wiki/
Embedding mindmaps in a wiki - WikkaWiki, a GPL-licensed WikiEngine, provides native support for inline FreeMind? data and maps.