Mindmapping is something I use on a daily basis to capture information. Rather than linear note taking, I feel mindmapping fulfills my needs to take down random notes and is more useful in aiding recall even many years after the event! Therefore, a mindmapping software is an essential tool for me. I have been using Freemind to do mindmapping on the PC for about a year now. Although there are other mindmapping software on the market, Freemind is free and has all the features I need.
Unlike manual freehand mindmapping on a piece of paper, computer-based mindmapping frees you from having to think where to put in new branches of thoughts or infomation even if the screen is full. There is always space as the software automatically figures out to rearrange or re-size the screen to fit in more information.
It has colorful icons, clouds, links, annotations to make you highlight ideas and information, to make you remember better even after a long period of time has passed. Additionally you can link nodes of information to external files such as diagrams, pictures, sound recordings, movies, text documents and even other mindmaps.
I've used Freemind in presentations instead of the normal Powerpoint if the presentation is free flow, i.e., doesn't require a linear flow. The ability to link to other files is a great plus point for this great piece of freeware. I totally recommend you try out Freemind (http://sourceforge.net/projects/freemind/). The use of this software is only limited by your imagination.