Two awesome but not yet perfect (until–hint! hint!–they support links that can self-refer) concept mapping tools are VUE (Visual Understanding Environment) and IHMC CmapTools, both fairly cross-platform software packages. IHMC CmapTools supports built-in social tools and cloud storage, but VUE is not bad either. Both have some nice presentation tools and good export formats (with just a few hiccups). As an example of what you can do, I present the Rock Cycle diagram we use in my class. Unfortunately, I constantly think of new arrows to add on the diagram, and I’m not 100% satisfied with the terminology on the arrows. I.e. it could use some refinement. I would appreciate comments from geologists or Earth Science teachers.