Concept maps visually display relationships of information items.
Kelvin's Concept Mapping Tutorial
Concept Map about Concept Maps
What are the steps in building a concept map?
"The Theory Underlying Concept Maps and How to Construct and Use Them", Joseph D. Novak & Alberto J. Canas, Florida Institute for Human & Machine Cognition
Concept Mapping (Web Center for Social Research Methods)
Concept Mapping Tutorial (University of Surrey) [link broken 2/10/14]