Ubuntu is available free of charge and you get a CD of the latest version (8.10 (Intrepid Ibex) with no extra cost
FOR UBUNTU
https://shipit.ubuntu.com/
FOR KUBUNTU
https://shipit.kubuntu.org/
FOR EDUBUNTU
https://shipit.edubuntu.org/
8.10 is not actually being shipped yet, it is a pre-release order form, but when it is available will be the "full" version.