A couple off months ago I went to course to learn mind mapping.
I found it to be very useful to remember things in a much more efficient way then taking “classical” notes. I can recommend it to everybody. I use whenever I can.
Until recently I just used a pencil and a notebook, but a couple of days ago found some open source software on SourceForge. I found this software very useful, because now it is much easier to manage my mind-maps and I don’t run put of paper anymore. 
Of course it was very easy to install on Gentoo, because there is an ebuild provided via portage