Manage your installed personas (lightweight themes).
F.B. Purity hides the ads, app spam and other annoying clutter from your facebook news feed, lets you increase the font size, change colours plus many more features and generally makes Facebook a lot less annoying to use.
Preview lightweight theme when hover on menuitems in Apply Theme menu.
Prevent duplicate tabs. Allow only one tab for a url. If you click a link that is already opened in a tab, then existing tab would be focused instead of opening a new tab. This works even across firefox windows.
Dynamic creation of bookmark-style toolbar buttons which you can customize.
TaQuilla Requires Restart
Automatic tagging using Bayesian statistics
ThreadKey Requires Restart
Strike the 'T' key to sort messages by thread, strike the 'U' key to sort them unthreaded again, just like the 'G' key switches to Grouped By Sort view
jQuery Requires Restart
jQuery and jQuery UI embedded in browser
Zorcher Requires Restart
Selecting a small text on the page do not need to copy it into the search bar of your browser or search engine. Just press the right mouse button and select the search service from the available list.
RC Print Requires Restart
Adds a "Print" option to the Right-Click context menu.
Google Redesigned 2 Requires Restart
Ported version from Firefox to be compatible with Seamonkey 2.
A complete redesign of popular Google services, Google Redesigned changes the appearance of popular Google services.
Scriptish Requires Restart
The greatest user script engine on the Internet (a fork of Greasemonkey).
When you press the middle mouse button or scroll wheel mouse show popup window the history in the url bar and search bar.
Adds toolbar buttons for each restartless add-on (including user scripts and plugins) to toggle its enabled state.
This 15KB restartless add-on will add a "File" -> "Restart" menu item and a ctrl/cmd + alt + r hotkey to restart Firefox or Seamonkey.
WebPG for Mozilla Requires Restart
An extension which provides GnuPG/GPG/PGP related functions to Moizilla Firefox, Thunderbird and Seamonkey
SM Home Button Requires Restart
Navigation bar Home Button (resurrected by sailfish)
FolderFlags Requires Restart
Allows users to edit the flags Thunderbird sets on folders.
Forecastfox Weather Requires Restart
Get international weather forecasts from AccuWeather.com and display them in any toolbar or statusbar with this highly customizable and unobtrusive extension.