I've watched hundreds of documentaries...really love them. Some good ones that are perhaps interesting to a backpacking crowd....
Encounters at the End of the World (Herzog's beautiful exploration of Antarctica)
Deep Water (Amazing, suspenseful story about a fated boat trip around the world)
Touching the Void (mountain climbing story set in Andes)
Grizzly man (an instant classic...Herzog, again, is a great documentarian)