I think you may find Reconstructor useful. [INDENT]http://reconstructor.aperantis.com/[/INDENT] I tried it out and it worked pretty good. It was a bit scary, though, running the product as root.
I'm trying to do something similar. I want to create a custom version of Ubuntu that has a link to a video on the desktop. So I used Reconstructor to free up a bunch of space (the video is 100+MB) and then copied the video into /usr/share but I can't figure out how to add a link to it from the user's desktop, like the examples folder that normally shows up.
I've been searching & googling and doing a lot of investigation and learned a bit about the Ubuntu CD and other Live CDs. But I haven't been able figure out how add the link. There's probably some dpkg command I need to run or some package I need to tinker with.
Anyways, Reconstructor is the best thing I've found so far. It seems to automate the steps you find in the various HOWTOs (e.g. https://help.ubuntu.com/community/LiveCDCustomization).
I hope this helps. Good Luck... I'm gonna keep looking for my solution.
Update: The Reconstructor forums have been very helpful. I just need to add the link to /etc/skel.