Your question is not clear, so I have two answers, depending on what you are really asking.
To update an Internet-connected Ubuntu system with the latest packages: go to the System menu (top left of your desktop) and choose Administration/Update Manager. Click on "Install Updates". Alternatively (command-line option): open a terminal emulator and run:
sudo apt-get update; sudo apt-get dist-upgrade
To get an Ubuntu install CD with the newest packages: get a "daily build" install CD from here:
You can use this install CD to update the packages on a system that isn't connected to the Internet.
EDIT: Note that a "daily build" CD will have the very latest packages. If you want, say, an Ubuntu 9.04 install CD with the latest Ubuntu 9.04 packages, I'm not sure where you would go. The usual thing is to simply install 9.04 and then let the system update itself as I explained in the first part of the answer.
Your question is not clear, so I have two answers, depending on what you are really asking.
To update an Internet-connected Ubuntu system with the latest packages: go to the System menu (top left of your desktop) and choose Administration/Update Manager. Click on "Install Updates". Alternatively (command-line option): open a terminal emulator and run:
To get an Ubuntu install CD with the newest packages: get a "daily build" install CD from here:
http://cdimage.ubuntu.com/daily/current/
You can use this install CD to update the packages on a system that isn't connected to the Internet.
EDIT: Note that a "daily build" CD will have the very latest packages. If you want, say, an Ubuntu 9.04 install CD with the latest Ubuntu 9.04 packages, I'm not sure where you would go. The usual thing is to simply install 9.04 and then let the system update itself as I explained in the first part of the answer.
EDIT: Okay, did another Google search and found how to make a custom Ubuntu install CD. You can easily fold in the latest packages for a stable Ubuntu, or fold in your own special-purpose packages. Here's the URL: http://maketecheasier.com/reconstructor-creating-your-own-ubuntu-distribution/2008/07/05
And here is a direct link to the tool you use: Reconstructor
The Google search terms I used were "make your own Ubuntu distro".
EDIT: I also found another tool: UCK - Ubuntu Customization Kit