This page is also linked from the original http://www.ultimatebootcd.com page - MS is on his a$$ to change the domain name.
Excellent tools: http://www.windowsubcd.com/contents.htm
I have gotten a lot of use out of the original Ultimate Boot CD, but this takes the concept forward.
It takes a little time to put together, but I built and burned one this evening for my "bag of tricks". Looks like it'll be handy with all of the 0wned machines I've been fixing lately.
There's also a link on that site to another program called AutoStreamer http://www.autopatcher.com/autostreamer.html, which makes slipstreaming service packs into a bootable XP CD real easy.
I know that slipstreaming can be done from the command line, but this little app makes it simple - no fumbling syntax or commands... Plus the output is an .iso file which makes a bootable CD - no muss, no fuss.