The Internet Archive continues to compile various public domain and open source films: Moving Image Archive.
Some examples:
* Vintage cartoons from the 30s and 40s
* Old movie trailers (Sabucat)
* Feature films, mostly older b&w, but the occasional gem like Donen's Charade (Cary Grant, Audrey Hepburn) which went public domain since the producers apparently forgot to put a copyright notice on the original print.
