The most effective way to watch movies for free is to stream them online from services such as Redbox Instant, Amazon Instant and the free version of Hulu. However, these services largely focus on paid content, so their selections of free movies are limited.
Another option is Crackle, which is owned by Sony and features many Sony movies. Other services like MyLifetime and IndieFlix feature small genres of movies that have been approved for streaming by those services. YouTube contains old movies that have fallen out of copyright. Lastly, library patrons can always check out DVDs from their local libraries.