If you're like me you've installed Ubuntu as a Virtual Machine inside of your day to day OS using Sun xVM VirtualBox (By far the Easiest to use freely available VM tool - it just works). And if you're like me you were perplexed that for all your efforts you couldn't easily adjust the screen resolution of the Ubuntu VM.
That is until you read either this post - or the post I link to: Installing Guest Additions for Ubuntu
I'm not going into all the specific details of this operation (the link provided does a good job). But, basically, once you've got Ubuntu running inside of Sun xVM Virtual Box you need to take one more step. If you click the menu item shown in the screen cap, Ubuntu will open its file browser exposing the location of the Guest Additions available to you. Once you know where they are, you pop open a terminal - cd to that location and run the Guest Addition .run file that matches your host OS.
After that you can reboot Ubuntu - and you will have the following: