Hattrick Livefox
- Lets you watch live games of the Hattrick online football game.
- http://hattricklivefox.mozdev.org/

Fission
- Combines address bar and progress bar, like Safari.
- http://mozilla.zeniko.ch/fission.html

userChrome.js
- Run Javascript like an extension without building a new one.
- http://mozilla.zeniko.ch/userchrome.js.html

Interclue
- Provides a content summary of a webpage when hovering over a link. Including statistics, metadata, sizes and other relevant information.
- http://interclue.com/

AnyKey
- Allows typing into phonetic Russian, Ukrainian, Amharic and others, transforming translit into the chosen language.
- http://anykey.mozdev.org/

AutoCopy
- Transfers text to the clipboard as soon as it's highlighted.
- http://autocopy.mozdev.org/

Copy URL +
- Copy to the clipboard the current document's address with additional information.
- http://copyurlplus.mozdev.org/

Send Tab URLs
- Emails the URIs of all browser tabs.
- http://aecreations.mozdev.org/sendtabs/

XHTML-MP
- Allows render HTML content with the mime-type of application/vnd.wap.xhtml+xml.
- http://xhtmlmp.mozdev.org/

Javascript Command
- Tools for writing/testing javascript on Firefox windows, web pages, and bookmarklets. [Require Login]
- https://addons.mozilla.org/en-US/firefox/addon/5058

Clippings
- Saves and manages frequently-entered text for later pasting into forms and input fields.
- http://clippings.mozdev.org/

/Find Bar/
- Adds Regular Expressions to the find bar.
- http://www.oxymoronical.com/web/firefox/FindBarRX

ErrorZilla
- Adds an image to the error page for down domains with helpful buttons.
- http://www.jaybaldwin.com/News.aspx?id=51

Menu Manipulator
- Allows you to move, edit, or create new <menu>, <menuitem>, and <menuseparator> elements within a <menubar>, <popup>, or the <tabbrowser>s context menu.
- http://forums.mozillazine.org/viewtopic.php?t=272717

ShowIP
- Show and query the current IP Address in the statusbar.
- http://l4x.org/frontpage/showip

Tabs Menu
- Adds a Tabs menu to the main menu that lets you easily change between open tabs.
- http://mikelward.com/software/firefox/tabs-menu

TabSearch
- Type keywords, and only the matching tabs will remain showing.
- http://www.semicomplete.com/projects/firefox-tabsearch/

YesScript
- Allows blacklist JavaScript from defined domains.
- https://addons.mozilla.org/en-US/firefox/addon/4922

X-Ray
- Shows the tags on a page without viewing the sourcecode.
- http://www.designmeme.com/xray/

Text Formating Toolbar
- Allows easy formatting of posts on forums, blog comments and wikis.
- http://codefisher.org/toolbar_button/format_toolbar

SwiftTabs
- Allows you to assign shortcuts to tab switching and closing.
- http://heygom.com/extensions/swifttabs

Menu Editor
- Allows you to customize the menus in Firefox and Thunderbird.
- http://menueditor.mozdev.org/

CookieSwap
- Maintain multiple cookie profiles and switch between them on the fly.
- http://cookieswap.mozdev.org/

ChromaTabs
- Tints browser tabs with a color specific to the website loaded.
- http://labs.mozilla.com/2006/11/chromatabs/

Development Resources & Extensions
- Extensions directory and resources for extension developers.
- http://www.extensiondevelopment.org/

All-In-One Sidebar
- Helps view dialog windows such as downloads, extensions, and view source or websites in the sidebar.
- http://firefox.exxile.net/aios/

BlogThis
- Adds right-click access to Blogger's BlogThis popup.
- http://weblog.philringnalda.com/2004/09/17/updated-right-click-blogthis-for-firefox-and-mozilla

ScreenGrab!
- Save or copy the current page, viewport or selection in a png file.
- http://www.screengrab.org/

User Agent Switcher
- Adds a menu to switch the user agent of the browser.
- http://chrispederick.com/work/user-agent-switcher/

Bookmarks Synchronizer
- Bookmarks Synchronizer is a Mozilla Firefox extension that allows to synchronize bookmarks via an FTP server.
- https://addons.mozilla.org/firefox/2367/

Sogame Extensions
- Developer site including the extensions: Define, Dummy Lipsum, Extension List Dumper, NewTabURL, searchOnTab, Tab To Window, TimeStamp Converter and withAttach.
- http://sogame.awardspace.com/

Tabinta
- Lets insert tab characters in multi-line text input fields.
- http://tabinta.mozdev.org/

Glubble
- Creates a trusted surfing environment for kids. Allows you to set sites that you trust for your kids, comes with a starter pack.
- http://www.glubble.com/

SiaC - Share-in-a-Click
- Share websites you like with your friends, with a click on a toolbar button.
- http://www.shareinaclick.com/

FireGPG
- Brings an interface to encrypt, decrypt, sign or verify the signature of text using GnuPG.
- http://firegpg.tuxfamily.org/

Torbutton
- Enable or disable the browser's use of Tor, which stands for "the Onion Router", a system providing strong anonymity. Also works with Thunderbird.
- http://freehaven.net/~squires/torbutton/

FireFTP
- A free, secure, cross-platform FTP client.
- http://fireftp.mozdev.org/

Font Finder
- Displays relevant CSS styling (font-family, color, font-size, etc) for any selected text.
- http://www.bendodson.com/extensions/fontfinder/

AddArt
- Replaces advertising images on web pages with art images from a curated database.
- http://www.addart.eyebeam.org/

SpiderZilla
- Allows to download an entire website from the Internet to a local directory, copying recursively the structure and all the content.
- http://spiderzilla.mozdev.org/

NoScript
- Blocks all scripts on a page unless it is from a site whitelisted by the user.
- http://noscript.net/

Flashblock
- Blocks all Flash content in a web page from loading automatically and allows selective activation and whitelisting of sites.
- http://flashblock.mozdev.org/

ChatZilla
- A simple, straightforward Internet Relay Chat (IRC) client.
- http://chatzilla.hacksrus.com/

Session Manager
- Saves and restores the state of all windows, either when you want it or automatically at startup and after crashes.
- http://sessionmanager.mozdev.org/

Locationbar²
- Puts emphasis on the domain and decodes URLs for better readability.
- http://en.design-noir.de/mozilla/locationbar2/

Link Evaluator
- Evaluate the availability of on-line resources.
- http://evaluator.oclc.org/

Adaptive Referer Remover
- Blocks referrer URLs from being sent by headers using regular expressions.
- http://misccs.dyndns.org/index.php?Adaptive%20Referer%20Remover

Foxmarks Bookmark Synchronizer
- Automatically synchronizes your bookmarks between two or more computers running Firefox. Includes a feature to access your bookmarks from any computer.
- http://www.foxmarks.com/

Arantius - TinyMenu
- It merge selected menus for the main menubar into a single menu.
- http://trac.arantius.com/wiki/Extensions/TinyMenu

Multiple Tab Handler
- Add the ability of select multiples tabs at once by dragging the mouse. Features close, reload, bookmark or copy URIs commands.
- http://piro.sakura.ne.jp/xul/_multipletab.html.en

Extension Hunter
- Bill's list and users picks of Firefox 2.* compatible extensions.
- http://www.extensionhunter.com/

Link Widgets
- Eases navigation within sequences of pages by providing toolbar buttons for the first, previous, next, and last page.
- https://addons.mozilla.org/firefox/2933

Bookmarks LinkChecker
- Detects updated, redirected and broken links in bookmarks list by adding icons within the drop-down bookmarks menu.
- https://addons.mozilla.org/firefox/1647

Linkification
- Converts text links into clickable links.
- http://yellow5.us/firefox/linkification/

MozBraille
- Self-voicing and Braille output based on the Mozilla browser.
- http://mozbraille.mozdev.org/

Link Alert
- Changes the cursor to indicate the type and target of a link.
- http://linkalert.googlepages.com/

Optimoz - Mouse Gestures
- Execute commands without using the keyboard, menus or toolbars. Instead, the user holds down a mouse button (usually the right one), moves the mouse in a certain way to form a gesture, then releases the mouse button.
- http://optimoz.mozdev.org/gestures/

Linky
- Aims to increase the user's power to handle links in Mozilla.
- http://gemal.dk/mozilla/linky.html

Add-ons Mirror
- Formerly known as The Extensions Mirror. Forum featuring information about a variety of extensions.
- http://forum.addonsmirror.net/

Piggy Bank
- Piggy Bank is an extension to the Firefox web browser that turns it into a “Semantic Web browser.”
- http://simile.mit.edu/wiki/Piggy_Bank

LiveClick
- Enhance Live Bookmarks with links to home pages, favicons, notifications and other feed reading features.
- http://liveclick.mozdev.org/

Migemo
- Provides a feature to find Japanese terms in roman-letter spelling.
- http://piro.sakura.ne.jp/xul/_xulmigemo.html.en

Paste and Go 2
- Useful paste and go, paste and search added to search and location bar context menu.
- http://pasteandgo2.mozdev.org/

Split Browser
- Splits the content area of the browser window as you like. Status of split browsers are saved, and automatically restored on the next startup.
- http://piro.sakura.ne.jp/xul/_splitbrowser.html.en

Long Titles
- Prevent long tooltips from being cropped by displaying them on several lines.
- http://home.etu.unige.ch/~robin0/LongTitles_en.html

MultiSidebar
- Use multiple sidebars simultaneously.
- https://addons.mozilla.org/firefox/4534

LiveHTTPHeaders
- Adds various functions for handling HTTP Headers.
- http://livehttpheaders.mozdev.org/

FaviconizeTab
- The width of the specified tab becomes small up to the size of favicon.
- https://addons.mozilla.org/firefox/3780

BBComposer
- Universal WYSIWYG editor for Firefox, allows edit textareas in those languages: XHTML/CSS, BBCode, Mediawiki, HTML and XBBCode.
- http://bbcomposer.elitwork.com/home.html

Tamil Key
- A utility for typing in Tamil language.
- https://addons.mozilla.org/firefox/2994

MR Tech Local Install
- Provide several tools to install and manage extensions and themes locally.
- http://www.mrtech.com/

Firefox Showcase
- Shows tabs as thumbnails, to preview, manage and search across them.
- http://showcase.uworks.net/

Split Pannel
- Open a panel next to main browser area (similar to a sidebar) with current URL.
- https://addons.mozilla.org/en-US/firefox/addon/3275

CLiCk, Speak
- An open source extension designed for sighted users who want text-to-speech functionality.
- http://clickspeak.clcworld.net/

Fire Vox
- An open source suite of extensions that turn Firefox into a talking browser for the visually impaired.
- http://www.firevox.clcworld.net/

Adblock Plus
- Blocks advertising, banners and other unwanted stuff on websites.
- http://adblockplus.org/

Launchy
- Adds a menu to open different types of links like images, emails, ftp, audio, video and many others with external applications. Includes overview, customization details, version history and screen-shots.
- http://gemal.dk/mozilla/launchy.html

Google Extensions
- Includes the Google Toolbar, Google Browser Sync, Google Notebook, Blogger Web Comments and Google send to phone.
- http://www.google.com/tools/firefox/

Tab Mix Plus
- Enhances Firefox's tab browsing capabilities with lots of options.
- http://tmp.garyr.net/

SubmitToTab
- Direct the submission of a form to a new tab.
- http://dragtotab.mozdev.org/submittotab/

Organize Status Bar
- Add the ability of organize the statusbar icons.
- http://yellow5.us/firefox/osb/

IE Tab
- An extension from Taiwan, embeds Internet Explorer in a Mozilla/Firefox tab.
- http://ietab.mozdev.org/

Download Statusbar
- Allows to keep track of ongoing and completed downloads in a statusbar.
- http://downloadstatusbar.mozdev.org/

Fasterfox
- Performance and network tweaks for Firefox.
- http://fasterfox.mozdev.org/

SwitchProxy
- Switch between multiple proxy configurations quickly and easily.
- http://mozmonkey.com/switchproxy/