From reading http://ubuntuforums.org/showthread.php?t=46758 and looking at http://archive.ubuntu.com/ubuntu/pool/main/o/openoffice.org2/, I'd suggest trying to install the package "openoffice.org2"
As the root user in a shell, do something like:
aptitude install openoffice.org2
Just to confirm this (found a laptop with ubuntu on it): Assuming you're running Ubuntu Hoary (5.04), you will need to add the 'universe' repository. You can do this by editing /etc/apt/sources.list and putting the word 'universe' at the end of the line that looks approximately like deb http://archive.ubuntu.com/ubuntu hoary main restricted The 'archive.ubuntu.com' might be different, depending on which mirror you are using. Once you've added universe, run aptitude update in a console to update your database, then run aptitude install openoffice.org2 I believe synaptic is a semi-decent GUI for apt, so you might like to try this instead.