The Public Domain Review showcases a growing collection of films, mainly from the Internet Archive. Categories include : Clips · Shorts · Silent Features · Talkie Features Animation · Comedy · Drama · Thriller/Noir · Horror · Fantasy/Adventure · Documentary · Ephemeral;which can be also be filterd by decade/period. Each film is supported by useful notes and comments. which will be helpful for further research.
I would suggest; if you are remixing video - this would be an excellent source from which to draw content. It also features a very early remix - Charles A. Ridley's - Nazi Style Lambeth Walk.