The data used for this is available from the National Library of Medecine's Visible Human Project; see this page for instructions.
All the command examples (in mono-spaced font on the following pages) assume that you are in the directory where you have a few gigs of spare disk space, as cropped copies of the slices will be put there.
The command examples also assume that the all the compressed slice images for the head (such as avf1054b.raw.Z) can be found in a directory called "data/"; whether this is a symlink or a real sub-directory is not an issue. All the PNG images generated will be put in another sub-directory (or link to one), called "doc/". This was more for my benefit, so that I could update the documentation easily as I created the examples.
One alias used in many of the examples is for making a PNG image with ImageMagick's convert program:
alias topng "unu save -f pnm | convert PNM:- "
If you plan on following along by executing all the commands that are included on each page, be sure to run them all, and to run them in order. Various files and aliases are set up in earlier stages that will be used at later stages.