The alternate CD can be found on the same download page:
http://www.ubuntu.com/getubuntu/download
But you need to check the box at the bottom.
The alternate CD has more flexibility. It is briefly discussed here:
https://help.ubuntu.com/community/Installation
and here: https://help.ubuntu.com/community/GettingUbuntu
and more detailed here: http://releases.ubuntu.com/8.04/