After much waiting and anticipation, Firefox 3 is officially launched. If you have installed the previous beta and release candidate version, simply run the Update manager (System->Administration->Update Manager) to upgrade to Firefox 3.
For those who have not installed Firefox 3, you can do it by adding the following package to your repository.
gksu gedit /etc/apt/sources.list
Add the following line:
deb http://ppa.launchpad.net/fta/ubuntu hardy main
Save and exit.
sudo apt-get update
sudo apt-get upgrade
Once finished, you should have Firefox 3 running in your Ubuntu.
(Alternatively, if you are patient enough, you can wait for Ubuntu to update their repository. It may take a while)