I thought it was time to share my own list of Firefox extensions that I use (I constructed this list using the Extension List Dumper, which I used to help me move from Firefox 2 to Firefox 3 by identifying the extensions I needed to update or replace).  I currently have 42 extensions installed.

• Aardvark 2.97
  http://karmatics.com/aardvark/
  Firefox 3.0 – 3.0.*
  Utility for cleaning up a page prior to printing, and for analyzing a page.
• About Menu 1.3.2.1
  Firefox 1.0 – 3.2a1pre
  Easily access the various About menus in Firefox.
• AboutPlug 1.4
  http://www.jasnapaka.com/mozilla/aboutplug/
  Firefox 1.5 – 3.1b3pre
  Adds link to about:plugins to menu Help
• Back To Google 1.2
  http://www.arikv.com
  Firefox 1.4 – 3.1b2
  Go back to your last Google results page.
• Bookmark Duplicate Detector 0.7.2
  http://bookmarkdd.mozdev.org/
  Firefox 1.0 – 3.0.*
  Helps you find, move and remove duplicate bookmarks. It also notices you when you are adding a bookmark already in your Bookmarks.
• ChromaTabs Plus 2.1
  http://garycalpo.wordpress.com/chromatabs-plus
  Firefox 3.0 – 3.0.*
  Colors browser tabs based on contents.
• Console² 0.3.9.1
  http://console2.mozdev.org/index.html
  Firefox 1.5 – 3.2a1pre
  The next generation error console.
• Delicious Bookmarks 2.1.018
  http://delicious.com
  Firefox 2.0 – 3.1b2pre
  Access your bookmarks wherever you go and keep them organized no matter how many you have.
• Diigo Bookmarks and Web Annotations 3.1.6.13
  http://www.diigo.com/
  Firefox 2.0 – 3.1b2
  Bookmark, highlight, and add sticky notes on any web page. Save your bookmarks on the web so you can access them anywhere.
• Domain Details 2.4
  http://dndetails.com/
  Firefox 2.0 – 3.1b2
  Displays Server Type, Headers, IP Address, Location Flag, and links to Whois Reports
• Download Statusbar 0.9.6.4
  http://downloadstatusbar.mozdev.org/
  Firefox 3.0a8 – 3.2a1pre
  View and manage downloads from a tidy statusbar
• eMusic Toolbar 1.5.47.1
  http://www.conduit.com
  Firefox 1.0 – 3.0.*
  More than just a toolbar.
• Extension List Dumper 1.14.1
  http://sogame.awardspace.com/
  Firefox 1.5 – 3.1b2
  Dumps a list of the installed extensions.
• Fire Analytics 1.26
  http://telega.phpnet.us/analytics/
  Firefox 2.0 – 3.1a2pre
  View Google Analytics reports in Firefox
• Firebug 1.3.3
  http://www.getfirebug.com/
  Firefox 3.0 – 3.0.*
  Web Development Evolved.
• Firefox PDF Plugin for Mac OS X 1.0.1
  http://code.google.com/p/firefox-mac-pdf
  Firefox 3.0 – 3.1b2
  Displays PDF documents in the browser.
• Fission 1.0.3
  http://mozilla.zeniko.ch/fission.html
  Firefox 3.0 – 3.1b3pre
  Progress bar in the address bar (Safari style).
• Force Content-type Lite 0.1.0
  Firefox 3.0 – 3.0.*
  Enable to reset Http header for downloading
• Forecastfox 0.9.8
  http://forecastfox.mozdev.org/
  Firefox 2.0 – 3.1b2
  Get international weather forecasts and display it in any toolbar or statusbar with this highly customizable extension.
• FoxyTunes 3.0.4.1
  http://www.foxytunes.com/
  Firefox 2.0 – 3.0.*
  Control any media player from Firefox and more…
• Greasemonkey 0.8.20090123.1
  http://www.greasespot.net/
  Firefox 1.5 – 3.1b3
  A User Script Manager for Firefox
• GridFox 1.1
  http://www.puidokas.com
  Firefox 1.5 – 3.1
  Displays a grid on top of a website.
• Group/Sort Tabs 1.1.4
  Firefox 3.0 – 3.0.*
  This extension adds group and sort support to tabs in Firefox.
• JSView 2.0.5
  http://forum.softwareblaze.com
  Firefox 2.0 – 3.2a1pre
  View the source code of external stylesheets and javascripts.
• LinkedIn Companion for Firefox 3.1.2
  http://www.linkedin.com
  Firefox 2.0 – 3.0.*
  Accelerate your business and career through LinkedIn
• Live HTTP Headers 0.14
  http://livehttpheaders.mozdev.org/
  Firefox 0.8 – 3.0.*
  View HTTP headers of a page and while browsing.
• Lola 0.3
  http://www.stream18.com/
  Firefox 1.0 – 3.0.*
  Web Development Tool
• Power Twitter 1.03
  http://83degrees.com/projects
  Firefox 1.5 – 3.0.*
  taking Twitter up a notch!
• ScribeFire 3.2.3
  http://www.scribefire.com/
  Firefox 2.0 – 3.1b3pre
  A full-featured blog editor that integrates with your browser and lets you easily post to your blog.
• Show Anchors 2.1
  http://www.pcdingo.net
  Firefox 3.0 – 3.0.*
  Show and catch anchors in page quickly
• Show my Password 1.7
  http://netcat.ath.cx/extensions.html
  Firefox 1.5 – 3.2a1pre
  Shows your password in readable letters
• Sothink Web Video Downloader for Firefox 5.1
  http://www.web-video-downloader.com
  Firefox 1.5 – 3.0.*
  Catch video files from the Web page.
• Squidoo 2.0.7
  http://www.squidoo.com/
  Firefox 1.0 – 3.0.*
  An extension for Squidoo Lensmasters
• stopwatch 1.0
  http://mutacia.net/
  Firefox 1.5 – 3.0.*
  real dual stopwatch
• StumbleUpon 3.28
  http://www.stumbleupon.com/
  Firefox 1.0 – 3.1b3pre
  StumbleUpon Toolbar
• SyncPlaces 3.4.1
  http://www.andyhalford.com/syncplaces/index.html
  Firefox 3.0 – 3.2a1pre
  Synchronizes bookmarks with your own web or ftp server
• Tab X 2.0
  http://clav.mozdev.org/
  Firefox 2.0 – 3.0.*
  Makes every tab always have a close button
• Tamper Data 10.1.0
  http://tamperdata.mozdev.org
  Firefox 2.0 – 3.0.*
  View and modify HTTP/HTTPS headers etc. Track and time requests.
• TinyURL Generator 1.0.3
  Firefox 1.5 – 3.0.*
  An extension to generate a TinyUrl in the background of any webpage
• Twittin Secrets Twitter Tips Toolbar 1.5.48.2
  http://www.conduit.com
  Firefox 1.0 – 3.0.*
  More than just a toolbar.
• WordPress Helper 1.0.2
  http://www.schloebe.de/firefox-extensions/wordpress-helper/
  Firefox 2.0 – 3.2a1pre
  Helpful WordPress developer-relevant tools and docs for Firefox.
• YSlow 1.0.2
  http://developer.yahoo.com/yslow
  Firefox 1.5 – 3.1b2
  Make your pages faster with Yahoo!’s performance lint tool.