Of all the films I have watched this year, the three most interesting and memorable where all documentaries. These three movies are The Corporation, Fahrenheit 9/11, and Super Size Me. Throw in Control Room into the mix, and you have a pretty exicting race for next year's best documentary feature at the Academy Awards.
Rather than review the movie here, I will re-direct you to a couple sites dedicated to this task:
IMDB, which currently has The Corporation rated at 8.5.
Rotten Tomatoes, which lists the Corporation as 93% fresh.
Here is a write-up by A.O Scott from the New York Times (Registration Required)
Personally, I rate this documentary as the most important movie to be released in our generation. Similar in impact to Fahrenheit 9/11, the most important role this film can play is to raise awareness of the important issues our society faces.