I just discovered the site snagfilms.com that let's you watch full-length documentary films for free.
The first one I watched (and will now take off my NetFlix rental list) was SUPER SIZE ME. That's Morgan Spurlock's look at the American obesity epidemic. He interviews experts nationwide and then put himself on a “McDonald’s only” diet for thirty days straight. This is a Sundance award-winning feature that is entertaining, frightening and informative.
Not that this site is designed for educational media use (there are commercial breaks), but you could use that particular film to talk about corporate responsibility, nutritional education, health issues, school lunch programs and other issues.
You can also put films on the web. You can embed a widget on your web site, which they call "opening a virtual movie theater" and become a "Filmanthropist" (since you are donating your pixels and supporting independent films). When you click on "info" on any widget, you learn more about that film and a related charity you can also support.