Really good documentary films?

I recently watched these and can recommend.....

American Experience: The Amish
http://documentaryvine.com/video/america...nce-amish/

Weather Underground
http://documentaryvine.com/video/weather-underground/

Hell and Back Again
http://documentaryvine.com/video/hell-and-back-again/

All of those are a great watch.

What's your favourite documentary?