Autoweight is a script designed for 3D Studio Max helping you speeding up the skinning process of characters and machines.
You define special polygon regions and the script finds the appropriate bones, calculates the appropriate skin-vertices and sets up smooth transitions between those regions.
There are also Youtube video tutorials explaining the script step-by-step.
The new version 1.0 comes with an installer so you don't need to hassle around with the mzp-stuff anymore.