Digital marketer or advertising planner or simply leading any type of plan or presentation, this free tool is no short of amazing. It’s compatible with all OSs and very simple to use. I used it from college days in 2006 and I still do now. That’s how great this tool is. I even use it personally.
More explanation here: http://freemind.sourceforge.net/wiki/index.php/Main_Page
And download options for your OS here: http://freemind.sourceforge.net/wiki/index.php/Download