A great (and long!) documentary on the making of one of my favorite movies:
Aliens is one of the few movies that has given me nightmares (aside from when I was a little kid and everything gave me nightmares). The first time I watched it was on VHS a few years after it came out, and I woke up sweating in the middle of night.
For my money, it is Cameron's best film. Despite all the fan hoopla around the director's cut and additional footage, I think the US theatrical cut is the version to watch. While there is some interesting stuff in the additional footage, none of it is really necessary, and mostly serves to draw out what is otherwise a textbook example of ruthlessly efficient storytelling.