Theme Font & Size Changer lets you change the global font size and font family used for the user interface in Firefox. Design your browser with your favorite font.
Translate the whole entire page or just a selection using Google Translate.
AiOS lets you open various windows as sidebar panels, and quickly switch between them. So it put an end to the window chaos! In addition to bookmarks and history it opens dialogues such as downloads, add-ons and more in the sidebar.
Allows Firefox to reload multiple images that failed to be displayed.
(former Google Dictionary and Google Translate)
In-line dictionary for any word you point to or double-click; whole page translation of any web page in another language.
Notifier for gmail, yahoo, hotmail, aol and more webmails.
X-notifier(aka WebMail Notifier) checks your webmail accounts and notifies the number of unread emails...
Supports : gmail, yahoo, hotmail, POP3/IMAP, facebook, twitter and more
YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages.
http://yslow.org is the official open source website.
Autofill Forms enables you to fill out web forms with one click.
Allows the download manager to also open in a tab or sidebar, and adds some optional display changes.