I think a good lesson one would be a tutorial on getting your dreamhack patched to the live version from a previous version. (I think this is documented in the wiki, but I felt intimidated by the process, and I'm a computer geek.) A nice option would be to be able to get a temporary D'hack of the last patch.

This would open all sorts of training opportunities, and also many cans of worms. The downside is all for our poor D'hack maintainer, but is significant workload; the upside is that trainees would be able to get a hack and then actually follow along with the steps of implementing a patch that's already been implemented in the live codebase. This is powerful learning mojo.

Alternately, it may already be possible using the repo to sync with a previous version, as opposed to the tip. I seem to recall seeing this option somewhere. If so, that would be a good starting point in the lessons, and would allow all the same training opportunities without overloading Madame Hackmeister. ;)