archive.org: Over 20,000 movies — free (and legal!)

No fooling.

Click on "Moving Images" here.

Just be sure you're don't have anything else to do today because once you start streaming or downloading movies that are either not copyrighted or have expired copyrights you may not be able to stop.

Vintage cartoons, Universal newsreels, films commissioned by the government during World War II — it's all here.

Note: Ann Hornaday, the Washington Post's movie critic, wrote, "Warning: This site is totally addictive for cinema history buffs."