I have *finally* gotten around to writing all this up. Teachers keep hounding me for it, so here it is! :)
This is how I go about doing my Greenscreen workshop. It covers the hardware I use, as well as the software. I'm a big fan of cheap / free software, as teachers are more likely to 'give-it-a-go' if there is very little outlay. Once you're confident, and your students are wanting to increase production value, you can upgrade to better software / cameras / lights etc.