Mind maps, as desribed on their wikipedia page, are a way of mapping or placing a graph structure onto a collection of data.
Items can be linked together with directed edges and with a label on the edge describing the relationship. Each data item at a vertex can taken on multiple tags (coloring) to describe their type.
If you have a Linux distribution that has the KDE (Kommon Desktop Environment, as opposed to the CDE Common Desktop Environment in Solaris) environment, you can see an implementation of mind maps in a note taking and note organizing software package
BasKet Notepads http://basket.kde.org/
The wikipedia page for BasKet is rather sparse and uninformative at http://en.wikipedia.org/wiki/BasKet_Note_Pads and does not really describe the full potential of the note organizing software.
The Mind Map software seems to be made for "rapid collaborating" and "brainstorming", very fuzzy words that seem to match the warm soft fuzzyness of the software. I have played with it, but it is poorly structured and not amazingly useful for organizing my research information.
It is, however, very useful for laying out quick hierarchical diagrams or tree diagrams. It does not easily allow one to export the graph structure in a useful and easy to reuse file format.