Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
The first and only download manager/accelerator built inside Firefox!
A customizable mouse gestures extension which enables to execute various commands and user scripts with six types of gestures.
Autofill Forms enables you to fill out web forms with one click.
Skips unnecessary pages on sites like Rapidshare, 4Shared, zShare, Mediafire, and more. Try it out, or watch a demo at http://www.skipscreen.com
Why click through ad-laden pages and wait for countdowns when your computer can do it for you
Polish spell-check dictionary for Firefox 2.0/3.0pre, Thunderbird 2.0/3.0a1 and SeaMonkey 1.1/2.0a1...
British English Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey by David Bartlett.
To enable, right-click in a multi-line text box, select "Languages", then "English / United Kingdom".