Krzysztof Lichota have made a set of tools for easy customization of Ubuntu
Ubuntu Customization Kit (UCK) is a set of tools for easy cutomization of Ubuntu Linux distribution (and its derivatives, like Kubuntu).
Currently it allows you to:
* Create bootable LiveCD with predefined languages based on original Ubuntu/Kubuntu live CD using wizard with GUI.
* Build live CD with special features using scripts. It is possible to customize root filesystem (for example install/remove packages), ISO contents (add/remove docs, change names) and initrd (add modules to boot, change boot sequence).
Currently UCK is a registered product on launchpad, so see there for bug reports and other information: https://launchpad.net/products/uck.
See it here