This is a full-length documentary that is included on the Halloween Blu-ray, and it's loaded with excellent information. Hardcore Halloween fans will absolutely want to check this out if they haven't already. It shows the entire process, from post-production to shooting, to the phenomenon that it has become.
It is filled with interviews with producers, the stars, and the director, and is the best documentary I've seen on one of my favorite horror films. My only complaint is that they show a ton of scenes from the theatrical cut, which, having just watched, was a bit redundant. On the flipside, they could have shown the full additional scenes from the TV edit that Carpenter put together instead. But, getting the chance to see any of those scenes was cool because I never had before.
I liked this documentary a lot, and it is highly recommended.