If you want support for MP3 files, Youtube video, and Java on your webpages, you could hunt down several packages - or just install the ubuntu-restricted-extras package install all the codecs and other files in one step. This also includes Microsoft core fonts.
sudo apt-get install ubuntu-restricted-extras
Eliminate Irritating Update Notifier Pop-Unders
This from Joseph Sinclair
In Ubuntu 9.04, update-notifier doesn't display an icon, it actually runs update-manager full-screen as a "pop-under". It's easy to miss, and there's no way to make it NOT run (so on a laptop, for instance, where stupid useless no-change updates are pending, you'll get the blasted thing running every time you boot, and quite often multiple times in a session).
There is a "magic" command to make it stop and go back to how it used to run (which you may have to run regularly since some updates seem to overwrite it), but it must be run for every user who can run updates:
gconftool -s --type bool /apps/update-notifier/auto_launch false
Adding that to /etc/bash.bashrc seems to be a quick-and-dirty fix that restores it for every user, and resets it if it gets overwritten. There's no guarantee this will work after the 9.10 update, but at least it works for now.