I have been a long time user of Firefox. In fact, I have been using it since it was named Phoenix. One of the best features of Firefox is it’s modular support for extensions. I have used so many extensions over the past few months, but here is a list of the top ones that I use daily:

Extensions
All-in-One Gestures – You just can’t be without mouse gestures
BugMeNot – Fills in login forms for websites that require free registration to read a single news story
ColorZilla – Great for developers. It allows you to sample colors out of your browser window and copy their RGB or hex color code
CuteMenus 2 – Adds nice icons in all the menus
Disable Targets For Downloads – Prevents download links from opening new blank windows/tabs
Download Manager Tweak – Heavy mod to the download manager. A must have.
Fasterfox – Performance and network tweaks for Firefox.
FirefoxView – Right click in IE and select “View in Firefox” to open that page in Firefox.
Forecastfox – Weather forecasts right in your status bar
Gmail Notifier – What else?
IE View – Right click in Firefox and select “View in IE” to open that page in IE.
ListZilla – Allows you to export theme and extension lists to HTML or Text files. Great for ensuring you got all your favorite extensions.
Minimize to Tray – Self explanatory. Probably my favorite extension.
Plain Text to Link – Converts plain text urls to Links
SmoothWheel – Smooth document scrolling
Tabbrowser Preferences – Tab management
Talkback – Crash reports to Mozilla
View Rendered Source Chart – Color coded source code chart. Makes traversing a page’s source much easier
Web Developer – Incredible toolbar. A must have for web developers.

Themes
Outlook 2003 Blue – My primary Firefox/Thunderbird theme. (Also available in Green and Silver)
ifox – My backup theme