I like concept maps - I used to make huge ones when I was a student - but they're the sort of thing that I think has never really made the transition to digital media. I think they just need bigger screens. And pencils, maybe. Geoff Cain: "I find myself thinking over and over again, quarter after quarter, semester after semester, how import tools like free writing, drawing, and concept maps are to thinking. However, I find that not all tools are created equal – especially when used in the wild." He lists a few: C-Map Tools, Inspiration, Lucid Chart, and CMap Cloud. Be sure to have a look at the slides at the bottom of the article.