To enable backports, go to your menu and select Applications > System > Software Sources.  You will be prompted to enter your password, and once the application is fully launched, click on the Updates tab, and place a check in the “Unsupported Updates (intrepid-backports)” box.  Once you’ve marked that box, click on the close icon.  You will be prompted to refresh your software sources, and new updates should then appear.  The upgrade to Xfce 4.4.3 should be included in that set of updates.

Of course, you could update your sources via the command line, too.  I need to run to the airport now, so I’ll leave well enough alone and assume that, if you’re interested in updating your sources list using the command line, you would know how to do so. 

Interested parties can view the Xfce 4.4.3 changelog here.

Here’s how you do it:

If you’re running Xubuntu 7.04 (Feisty Fawn), type: “sudo mousepad /etc/apt/sources.list” (without the quotes) and copy and paste the following lines to the bottom of your sources.list file:

# Xubuntu team personal package archive (Feisty Fawn)
deb http://ppa.launchpad.net/xubuntu-team/ubuntu feisty main
deb-src http://ppa.launchpad.net/xubuntu-team/ubuntu feisty main

Be sure to save and close your file once you are done.

Similarly, if you’re running Xubuntu 7.10 (Gutsy Gibbon), type “sudo mousepad /etc/apt/sources.list” (without the quotes) and copy and paste the following lines to the bottom of your sources.list file:

# Xubuntu team personal package archive (Gutsy Gibbon)
deb http://ppa.launchpad.net/xubuntu-team/ubuntu gutsy main
deb-src http://ppa.launchpad.net/xubuntu-team/ubuntu gutsy main

Again, be sure to save and close your file once you are done.

After you’ve saved the file, just type “sudo apt-get update && sudo apt-get dist-upgrade” into a terminal, and the Xfce packages in the Xubuntu PPA will be updated to their most recent versions. Enjoy.

[1] https://launchpad.net/~xubuntu-team/+archive