Despite only being released a few weeks ago, Ubuntu 8.10 (otherwise known as Intrepid Ibex) doesn't include the latest OpenOffice, 3.0.
If you want to upgrade, here's what you have to do:
Step 1: Add the repository, by going to system -> Administration -> Software sources and adding:
deb http://ppa.launchpad.net/openoffice-pkgs/ubuntu intrepid main
to your list of sources.
Step 2: Once that's done, type:
sudo aptitude update && sudo aptitude full-upgrade -y
And you're all set!
(Tip of the hat to Andre Gondim for the help!)