Let's get started with a simple one for a Friday. If you've worked in the corporate world, then obviously you love Dilbert.
The Daily Dilbert extension installs easily on your status bar and displays a little icon to click on. Click on the icon and presto! You get a Dilbert cartoon every day.
This very simple extension is great for your Dilbert fix. One feature I would recommend to the author is providing a mechanism to move back a day or two, kind of like a "< Previous" and "Next >" link. When I miss a couple of days of Dilbert, I get cranky. :-)