I stumbled across this at archive.org a couple of months back and it just occurred to me to share. Unfortunately the picture is very small, so it's usefulness as a reference is minimal. It's still very cool to watch.
WW1 moviesDespite the fact that it is a US Army Signal Corp film, it contains a lot of footage of other nationalities and even some supposedly captured u-boat footage. Some of it is rather suspect, though. For example, there is a shot that is labeled something like "A daring British patrol returns from a raid!" that shows a line of infantry trotting across a shelled field in broad daylight.
This isn't strictly speaking miniatures related, so I hope I'm not breaking any rules.