As a bit of a counterpoint to the rant in my last post about the last days of fair use, many movies have actually fallen out of copyright. Now, normally, nothing before 1920 will fall out of copyright in the foreseeable future, but the owners of some works failed to properly renew their copyrights. Archive.org lets you download entire feature films in MPEG formats of a variety of sizes. Here's their feature film section. Some of the famous ones I've found are His Girl Friday, which was notable for its fast-talking female lead, Plan 9 From Outer Space, notable for being labeled "the worst movie ever made" by most such lists :), and the original Night of the Living Dead.
So what's cool about these movies is not just that you can download and watch them for free; you're also free to splice and edit them and to use them in projects of your own, remixing them and making derived works.