After a lot of trial and errors, I've finally completed my script to customize Ubuntu Live CD, which can also be used to customize Live CD of Ubuntu based distros. I know, there are tools like UCK for customization purpose. But I wanted something simpler and easier. The result is "Customize It!".
Customize It! handles all cleanup operations and also regenerates the boot files required in case you changed the kernel. It also copies your package cache so that you don't need to download same files again. It has a straightforward syntax
customize-it [option] filename
In place of "filename", you need to provide the ISO filename.
The options could be,
-m, --manual manually customize the live cd
-u, --update update all packages in the live cd
-s, --script use external script "custom.sh"
-i, --install install to "/usr/bin" and exit
-h, --help show help message and exit
Manual customization option gives you a root shell inside the Live CD. All changes you do will be reflected in the Live CD. The update option only updates all packages installed in the Live CD. You can also use a script to automate the customization process. Just name it "custom.sh" and place in your home directory.
I've successfully used it many times. You can download it here.