The Ubuntu Font Family has been made default in Ubuntu 10.10, it can be downloaded from Launchpad and there are download links available on http://font.ubuntu.com too, yet the Ubuntu Font PPA is still private which makes it difficult for those not using Ubuntu 10.10 to stay up to date with the latest versions of the font.
So I've decided to make a PPA for Ubuntu 9.10 Karmic Koala and 10.04 Lucid Lynx users so they can easily install the Ubuntu Font Family and also receive updates (I'll backport each version in Maverick for Karmic and Lucid). Add the PPA and install the Ubuntu Font using the following commands:
sudo add-apt-repository ppa:webupd8team/ubuntu-font-family
sudo apt-get update
sudo apt-get install ttf-ubuntu-font-family
Like I said, the PPA currently holds packages of the Ubuntu Font Family for Ubuntu 10.04 Lucid Lynx and Ubuntu 9.10 Karmic Koala but on request, I can also upload packages for Ubuntu Jaunty (do we have readers still using Jaunty?).