Prelinger Archives holds approximately 11,000 digitized videos, primarily home movies and amateur films. Its goal is to collect, preserve, and facilitate access to films of historic significance that haven't been collected elsewhere. There is free access to many (but not all) films from the collection on the Internet Archive site.
Search the TED Talks library of videos filmed at TED conferences, TEDx events, and other events. Try narrowing your search to TED-Ed and view animated video lessons targeted to educators to use for customizing lessons.