Nodes, edges, and mental maps

What Martin, you have done here, is essentially creating mental maps or concept maps. It can be done using free tools such as Freemind, Mindmeister, and so on. Now, another way might be to use post-it notes (which lately I find very useful) and using the free post-it note app, you can take shots of the organisation, and then when you come back for revision, you can reorganise everything.