Inside Job- about the financial crisis of 2008 and the residual effects
When we Were Kings- about The Rumble in the Jungle
Copyright Criminals- about the legality of sampling in music
Dogtown and Z-Boys- about the proliferation of skate culture
Cocaine Cowboys - the first one. Don't bother with the second one - it is absolutely garbage.
Triumph of the Nerds - older documentary, circa 1995. If you like geeky stuff you'll love it. Basically tells the story of the personal computer up until that point.
Children of the Secret State - about North Korea. VERY depressing but eye opening at the same time.
Chicken Hawk - story follows a few members of NAMBLA and how they live. It's another documentary from the 90s. There is no gore or graphic pics but what you hear will make you sick to your stomach. You can find it on YouTube.