I came across this resource again today as I was preparing some stuff to share. Thinking Maps are a brilliantly simple but incredibly well researched set of tools for visually representing thinking. I heard the author David Hyerle speak last year in Auckland and thought it was the most immediately practical and applicable new idea I had come across in my teaching career. The power of thinking maps to help children progress their ideas is amazing. These are more than just graphic organisers. The image (left) links you to the official site or you can also visit this link to another site with other resources.
The introductory video is worth watching for an overview.
The thinking maps software is also available and certainly looks interesting although I think I would introduce the maps on paper first before I had students using the computer. This one is well worth a visit.