I just want to do a shout out for a very nice diagramming tool I bumped into via a referral from my Twitter stream.
http://www.diagrammr.com lets you write simple English phrases that describe either relationships between entities/objects/concepts or interactions between them. For each sentence, the tool creates two nodes (subject and object) and a path between them (either a relationship or an interaction). You can easily share this, collaborate, or embed it, as below (just right-click on diagram and copy the image URL, and paste it into an img tag)
I can imagine even doing this live during a design walkthrough or presentation, to help make the learning more dynamic.
The web site doesn't say who the author is, but kudos to whoever they are, very creative and very simple. Thanks!