Firefox Extensions you can't live without
1. Tab Mix Plus: Allows you to control how you browse by opening tabs for events you specify. This gives you full control over what happens when you browse, and when new windows get opened, recycled, or new tabs get opened.
2. Forecast Fox: This allows you to show the weather in your status bar and is very customizable.
3. IE View: This adds an item to your right click menu that opens the current page in Internet Explorer. Some poorly designed pages require the use of internet explorer, and as a web developer I am constantly checking my pages in both browsers.
4. Gmail Notifier: Notifies you of new gmail through a popup box and a status bar symbol. Simple and useful.
5. Web Developer Extension: If you don't do web design, you don't need this. However, if you do, you need this more than you can imagine. My favorite feature is the "edit CSS" which allows you to play with a page's CSS in real time to see the changes. Other useful features are outlining block level elements, and turning off images.
6. Google Toolbar: This allows Easy searching of google news, froogle, google, images, and groups. It also has a very useful spell checker for web forms and displays search terms at the top of the page. You can click on them to jump to the point in the page where the term appears, which is useful for wordy pages.
7. BugMeNot: When you get to a site that requires free registration, you can right click on the login field and select bugmenot. This anonymously logs you in saving time and privacy.
8. Unread Tabs: Really simple. It italicizes tabs you haven't viewed yet.
9. Adsense Notifier: If you use google adsense to monetize your website, this statusbar extension will show you how much money you made today and the number of views and clicks.
10. Stock Ticker: Track your stocks in the statusbar or as a separate toolbar.
When you are done adding and tweaking all these plugins, you can easily backup your configuration using MozBackup.