'For a long time I have dreamt of a "magical script" that could download packages of some other distro, cut them right down to Puppy-size, then build a Puppy Linux live-CD -- and do all of this totally automatically.'

Woof is a Puppy building program. It is used to build a Puppy Linux distribution from the binary packages of another Linux distribution.

The process used by Woof to build a Puppy Linux distribution from another Linux distribution:

The user selects the Linux distribution to be used as the foundation of the Puppy Linux distribution
The user selects the choice of packages and other options
The user initiates the build process
If needed for the selected Linux distribution, the scripts perform preprocessing tasks
The scripts download the package database files of the selected Linux distribution
The scripts download the package files of the selected Linux distribution
The scripts build the generic Puppy-packages
The scripts build the Puppy Linux live-CD .iso file of the Puppy Linux distribution
The user burns the Puppy Linux live-CD from the .iso file
If desired, the user builds a new variant of the Puppy Linux distribution using the CD-Remaster tool available in Puppy Linux

The Linux distributions that Woof can use as the foundation for a Puppy Linux distribution include: Debian, Ubuntu, Slackware, Arch, T2, SDE, Puppy, Mageia

Project version control management system is bones:
Bones official page
Bones on Barry's blog

What can be achieved using Woof: Wary, Puppy431, Dpup (Dpup, Squeeze), Upup (Puppy5, LupQ), Spup, Tpup (Fatdog64, Quirky)

The CD-Remaster program available in Puppy Linux is a simpler way yo build variants of the Puppy Linux distribution.

Official
Woof official page
Woof on Barry's blog

Tutorials
EZ-Woof-525 - The Lucid 5.2.5 Build Environment
How to Use Woof to Build Lucid Puppy 5.2 thread
How to Build a Custom Puppy with Woof thread

Other
Puppy Package Management on Barry's Blog
WikiPedia:Woof_(software)
Ppup 416alpha bug reports thread
Woof: working okay for me thread
How to switch kernels between Puppy versions thread