Nice introductory article from the author of Knoppix Hacks.

Knoppix is pretty easy to remaster and many people have created their own Knoppix variant to suit their needs. However there are a number of tweaks and changes you can make that don't require a complete remastering if you take advantage of the knoppix.sh script. I'll go over some of the advantages to this approach over a full remastering below.
http://www.onlamp.com/pub/wlg/5964