Downloading movies with an expired copyright?

So, a long time ago, I was able to download Charade from some website. It was completely legal on account of a copyright issue that put it in public domain. I wanted to go back there to see what other movies were available, but I can't remember what it was.

Does anyone know of a place where you can download movies that are public domain?

Possibly:

http://www.archive.org/details/movies

http://purchasemovies.net

http://download-cinema.net