Status bar widgets and progress indicators for Firefox 4+
The greatest user script engine on the Internet (a fork of Greasemonkey).
This 15KB restartless add-on will add a "File" -> "Restart" menu item and a ctrl/cmd + alt + r hotkey to restart Firefox or Seamonkey.
The Add-ons Manager slims down!
This add-on reduces the height of entries in the Add-on Manager, so you can display more of them at a time.
Stratiform is the ultimate user friendly customization add-on for Firefox. It puts the power in the average user's hands to customize the browser's look.
Bring back your personal and powerful Firefox Button!
Anti-Aliasing Tuner for Direct2D/DirectWrite Text Rendering
Adds icons to your Firefox menus. Choose from the built-in icon sets or import your own.
Add RSS icon back into location bar (URL) in Firefox 4.0. This icon was showed in Firefox 3.5/3.6 by default when page offered feeds.
Vertical Tabs for Firefox with a space-efficient native look & feel.