There are thousands of wonderful documentaries out there and quite honestly the main reason I have a Netflix account is so I can watch as many of them as possible. Here are a few that I've seen in the last few years that I would highly recommend. Almost everything by Michael Moore is also great, but these deal more with our environment and/or food supply!
Blue Gold
Earthlings
Earth 2050
Food, Inc.
GasLand
Homo Toxicus
Petropolis
Super Size Me
Tapped
Blue Gold
Earthlings
Earth 2050
Food, Inc.
GasLand
Homo Toxicus
Petropolis
Super Size Me
Tapped