UCK (ubuntu customization kit)powerful tool for customizing Ubuntu Iso. I have used this to customize my ubuntu 11.04 last week after the official release of Natty Narwhal. Installing Uck on ubuntu 11.04 is easier than before. Just Follow the Step and enjoy Uck on your Ubuntu Machine.
I prefer using uck .deb package rather than tar package.
If You got any dependencies problem install whatever asked by machine.
The last stable version of uck released was on 2011-04-04