Blog about tools for drawing diagrams--free ones as well as paid ones. I particularly like (Inspiration--$ because you can hyperlink and save as a Word document with hyperlinks too--as well as bubbl.us--free.
Grokking is new to me--looks like a powerful search possiblities that allows a mindmap of related terminology. You can create a teacher account, specify difficulty level, create graphs and more. Looks very interesting.
Great site for making mind maps and doing online brainstorming. Able to be exported and shared with others. Great tool for teacher collaborators and for kids! Super easy to use
CmapTools (free, of course) allow for the developing of concept maps and you can link to images, videos, documents, etc. Not quite as flexible as Inspiration (which is my favorite, but it costs money), but a good option.