So let me start off the list:
1) http://www.nliteos.com/ - This is a program that lets you customize your winxp install, from integrating service packs and hot fixes, drivers, disabling services, removing components from the install, integrating the unattend.txt file into the cd and more.
2) http://www.wpiw.net/The_Dark_
3) http://www.nu2.nu/pebuilder/ - This is BartPE it allows you to create what is called a Live cd of winxp, which is a bootable and installed version of XP on cd with any/all apps you want. This is useful as a troubleshooting tool when you can't boot into your computer, as you can install tools to fix problems from a windows environment and all its tools.
4) http://unattended.msfn.org/
5) http://www.msfn.org/ - A great resource for everything windows, specially when it comes to customizing. I highly suggest you create an account (its's free). Any doubts/questions can be answered here and there are tones of how-to's on many subjets.
Have Fun!!
Scott