PBS Frontline is the smallest and most selective of the free video options listed in this article. The site has over 150 documentaries and associated educational resources like study guides, transcripts, and additional interviews. The documentaries are all critical meaning that they deal with controversial and difficult topics: assisted suicide, the war on terror, religion, pornography, capital punishment, among others. Because it's PBS, the writing and technical quality of the films are top notch. You can search the films by category. My personal favorites on the site are Growing Up Online, The Persuaders, The Man Who Knew, and Is Wal-Mart Good for America?