Virus (復活の日 Fukkatsu no hi, literally "Day of Resurrection") is a 1980 Japanese post-apocalyptic film about the release and spread of a deadly virus. [more inside]
Full films for legal download: Archive.org has a large number of movies with expired copyrights for download. My favorite is 1936's Things To Come. Other nifty things include classic feature films like Battleship Potemkin and His Girl Friday, and shorts such as Max Fleicher's Superman, Three Stooges and Buster Keaton.