http://www.exploratree.org.uk/ 

a free online library of "thinking guides" you can either print out or use online. Templates include tracking an enqjuiry, the Futures Wheel, from a different angle, thinking boxes, compare and contrast, and a lot more. Each template is customisable; you can also use them to collaborate on projects with other people. 

http://www.visual-literacy.org/periodic_table/periodic_table.html 

Original and valuable presentation of many ways of seeing data, information, concepts and strategies.

http://www.mind-mapping.org/ 

Just about all the mindmapping, concept mapping and other graphical information organizers are covered there.  Also has articles about information mapping.

http://www.mindmapsearch.org/ 

Search engine that just looks at mind mapping sites or articles, and so produces highly relevant results.  Has categorized lists of such pages as well.

http://www.topicscape.com/mindmaps/ 

Directory of mind maps (hundreds) tagged and categorized.

http://www.nancymargulies.com/resources.htm 

Inspiration for information mapping.

http://www.wikimindmap.org/ 

Turn Wikipedia pages into mindmaps automatically.

http://en.wikiversity.org/wiki/Concept_mapping

Materials for learning how to use concept mapping

Jane Hart's Centre for Learning & Performance Technologies has a big list of mind-mapping tools.
Her reviews link back to reviews from many ed-tech-ucators around the world.