Thanks for telling us how a particular piece of software worked, I haven't gotten round to trying them all (maybe one day). Glad to hear it helped you out in your work presentation, I think the quality of freeware and open source has improved considerably over the past few years. I spotted this on my way here tonight, it isn't freeware but for $149.99 it's looks like a cheap ticket into the world of special effects, chromakeying and colour grading. It's called CompositeLab Pro, first time I've heard of it and it can be found at:
CompositeLab Pro - FXhome + 10' x 6' Green Screen
CompositeLab Pro 'professional grading and compositing for digital video'
You also get a 10 ft by 6 ft greenscreen thrown in with it.
$149.99
Watch the short demo video aswell to see what it can do.
I should point out I have no affiliation to any of the products or companies in this thread.