If you want to customize your Ubuntu or create your own version of Ubuntu, here's a list of tools you might need:
Ubuntu Customization Kit is a GUI tool that helps you customizing official Ubuntu Live CDs (including Kubuntu/Xubuntu and Edubuntu) to your needs. You can add any package to the live system, for example language packs, or applications.
Remastersys is a tool that can be used to do 2 things with an existing Debian, Ubuntu or derivative installation.
The power behind Reconstructor is the engine. Our open source engine provides the utility behind customizing and building a custom distribution. The engine (which is and always will be open source) is available on Github.
Live Magic is tool for end-users to quickly and easily generate their own Debian live systems.