In July 2006, a Japanese court ruled that all movies produced prior to 1953 were to be made available into the public domain. And so, many movies by Japanese director Akira Kurosawa were made freely available online, and most importantly legally. Those available on archive.org include Sugata Sanshiro (姿三四郎), They Who Step on Tiger's Tails (虎の尾を踏む男達), Stray Dog (野良犬), Rashomon (羅生門), Ikiru (生きる)
No doubt, the list I've present here is by no means complete and is likely to be further updated when reliable sources of the public domain films are made available. The sole film by Kurosawa that I would really like to see available soon is Seven Samurai (1954 - ouch, not really possible). I have not seen all of his movies, but my favourites so far are (in no specific order): Ran, Kagemusha, Seven Samurai, Rashomon.
Kurosawa's films have had a major influence on world cinema and continue to inspire filmmakers, and others, around the globe. "Seven Samurai" is frequently quoted as being one of the greatest and most influential films ever made, and has influenced modern filmaking in movies such as The Magnificent Seven, A Bugs Life, and Star Wars. Kurosawa's works are also influential to society in general. Most notably, the phrase "Rashomon Effect" has entered popular modern day usage indicating a conflicting situation.
Download the public domain movies by Akira Kurosawa here, available for free, courtesy of archive.org:
Format: 256Kb MPEG4 (Other formats are available on their respective sites)
Sugata Sanshiro (1943) - (195 MB) - site
They Who Step on Tiger's Tail (1945) - (149MB) - site
Nora Inu (Stray Dog (1949) - (313MB) - site
Rashomon (1950) - (226 MB) - site
Ikiru (To Live) (1952) - (367MB) - site