Here are two examples of Concept Maps from a quick google.
http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=RNWE,RNWE:2004-
15,RNWE:en&q=concept+map
http://www.graphic.org/concept.html
Concept Maps are an established technique within pedagogy (well, it has its
supporters, who are probably not very well supported).