An extremely simple, but extremely powerful tool for any class. Unlike the other two which would essentially be students assignments transferred to the teacher for marking, this one allows all the members of a class to engage in conversation about, well it can be just about anything. It’s something I still need to work out, but I can see the power of this, here’s a couple of examples that might better show what can be done.
One of the things that fascinated me about the last one was how the participation of others was encouraged. The strength of this seems to me to be that it can be a constantly evolving discussion between you and your students (and others if you so desire).