Tekzilla is a good place to find little tips, tricks, and hacks to make your computing experience better. In the video below, Tekzilla host Veronica Belmont shares a good tip for customizing the appearance of your Firefox browser.
Here are some other Firefox add-ons that may be of interest to you:
Cloudlet – Refine Google, Yahoo, and Twitter Searches
Quick Translation – Dictionary and Translation Firefox Add-on
Googlepedia – Google and Wikipedia Side by Side
Middle Spot – Visualize and Share Search Results
KidZui Gets a Firefox Extension and Offers a Free Version