Here are some links to articles on the visual representation of knowledge by Sigmar-Olaf Tergan, an academic leader in the field
This is a 1997 article by Eric Plotnick, from the ERIC Clearinghouse on Information and Technology Syracuse NY
For me, web research and concept maps are a good pairing. As I research - I build a map. As I map - I realise new areas that need research.
This papers variously by Arguedas, Cañas, Carnot, Carvalho, Dunn, Eskridge, Gram, Leake, Maguitman, Muldoon and Reichherzer have helped me to understand why, and see other possibilities.
This piece discusses the nature of knowledge, the difficulty in measuring achievement in the three types of domain knowledge, and how concept maps offer one way of judging students' knowledge structure.
Here is a link to a set of free templates for many types of mind maps. This is good solid stuff, and if you have MindManager, there's no reason not to get it.
But if you don't have MindManager, well, there's still no reason to hold back - go and pick up the MindManager Viewer
from MindJet's site. That is also free.