OK, maybe not 101, but I can think of at least six uses:
1) As a graphical way to capture goals and objectives during project initiation
2) For brainstorming solution ideas
3) To facilitate WBS planning and creation
4) To facilitate issues management in a more organized fashion
5) For brainstorming project risks
6) For capturing lessons learned throughout and after a project
Most mind-mapping software (which allows drag-and-drop functionality to sort ideas by category) is inherently easy-to-use, and allows for a quick and graphic way of sorting ideas and issues, especially when done in a group atmosphere.
Mind Manager from Mindjet is a good example, and it even exports to MS/Word, Powerpoint, and MS/Project. Check out their site below for more details...
Mindjet: Software for Visualizing and Managing Information