One of the machines I work on has a 15 inch monitor with 800 X 600 resolution. I occassionally use Excel 2007 & the ribbon almost takes up one third of the real estate. I was excited to find the Excel trick of hiding the Ribbon and having a minimalistic UI with just the Quick Access Toolbar, in the comments section of a blog posting.
To activate this feature, invoke the Customize Quick Access Toolbar menu that is next to the Office Button at the extreme top on the left. Click on the More Commands option to view list of commonly used & popular commands. Select your frequently used commands out of the complete list and they will then be displayed on the Quick Access Toolbar as buttons.
Use CTRL + F1 to minimize the Ribbon or toggle it back when required.