Restyle the web with Stylish, a user styles manager. Stylish lets you easily install themes and skins for Google, Facebook, YouTube, Orkut, and many, many other sites. You can even customize Firefox and other programs themselves.
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
We’re sorry to say we can’t maintain Skipscreen anymore. We’d love to see someone carry on with it. If you’d like to buy Skipscreen, or otherwise find it a good home, please contact us at firstname.lastname@example.org.
Show the IP address of the current page in the status bar. It also allows querying custom information services by IP (right click) and see location and avaiable vouchers for shopping sites. Additionally you can copy the IP address to the clipboard.
Official eBay add-on. Keep an eye on your eBay activity wherever you are on the web when you install the eBay Sidebar for Firefox. It’s a free tool built with eBay users in mind that will help you get more out of your buying and selling on eBay.
A compilation of some of the best Greasemonkey user scripts for YouTube in one interface.
Note from Mozilla: This add-on has been discontinued. Try Google Minimalist instead.
CustomizeGoogle enhances Google by adding information and removing unwanted information.