The first place I’d check

The first place I’d check is http://www.internetarchive.org for public domain ephemeral productions. So they have loads of newsreels from the war, the few war movies now in public domain and training or informational films. I have to watch myself when I visit the site. There is so much cool stuff, usually available in at least the quality needed for video CD’s (and sometimes DVD’s) that I start a download frenzy that can takes weeks to deal with. But I did put together a comic PSA using a variety of the films available for download & use. (Which reminds me, I should post it on my MySpace page.)

But anyway, for my money nothing beats the completely free internetarchive.org for value & variety of material available.

Good luck with your productions.