I've listed my most-frequently-used FireFox Extensions.
Hope that you find them useful:

1. All in one SideBar

All in one sidebar enables you to quickly access, organize, update, activate/passivate your extensions. Highly inspired from Opera web browser's sidebar.

You can also access your history, bookmarks, recent downloads, themes, JavaScript Console and Page Properties with just this very side bar.

I highly recommend you try it, if you haven't already done so:

2. Colorzilla

It assists web developers and graphic designers with color related tasks - both basic and advanced.

With ColorZilla you can get a color reading from any point in your browser, quickly
adjust this color and paste it into another program. You can Zoom the page you are viewing and
measure distances between any two points on the page.

Colorzilla is available for download here.

3. Dictionary Search

I am not a native English speaker. Although most of the time I can deduce the meaning of words from the general structure of the sentence; I often wonder the exact meaning of the word
(yeah I'm curious) and Dictionary Search is a great time-saver for me.

4. FireBug

I don't know how I had been developing AJAX applications without FireBug.

Some fun features of FireBug include;

• Logging for web pages
  
  No more 'alert("debug:" + myvar);' s in the source.
  Firebug logs them for you without interrupting the process.
  
  
• JavaScript debugging
  
  You can stop JS execution, add breakpoints, step in, step out from the methods.
  It's no different than using your favorite IDE's debugger.
  
  alert( "I will never ever use alerts for debugging again" );
  
  
• Errors at your fingertips
  
  FireBug adds a little icon to the Firefox status bar which tells you if your page is busted.
  No more digging through the muddy pile of errors in the JavaScript Console window.
  
  
• CSS / DOM inspector
  
  Elements and styles and events, oh my goodness. This can't be true. I can inspect anything on the page with my mouse. Morever I can change attributes, attach new events; modify/override JS methods! Unbelievable!
  
  
• JavaScript comamnd line
  
  To inspect and alter variables and state date.
  Sing with me:
  

  "No more alert debugging."

  
  
• Ajax Request Spy
  
  Logs all your XMLHttpRequests along with post data and header information on-the-fly.
  
  If you are developing (or you plan to develop) AJAX Web Applications; this feature is a must-have for you.
  

You can download FireBug from Joe Hewitt's web site.

5. FireFTP

Forget about your bloated FTP client. And meet FireFTP.

I assure you; you won't look for an alternative once you get used to it.

6. Web Developer Toolbar

A must-have for any Web Developer / Designer.

You had better use it to understand how an invaluable toolbar it is for the web developer.

7. Session Saver

Although FireFox is an excellent browser; it may crash once in a while.

If you are in the middle of a research with a zillion of tabs open (see the next list item);
then session saver is actually your life-saver. It saves all open sessions before the crash
occurs and loads them back when you re-launch Firefox.

8. TabMixPlus

If you are like me, a zillon tabs open side by side; then TabMixPlus is just the tool for you.

9. EditCSS

As its name implies, with EditCSS you are able to edit your site's CSS files on-the-fly and observe the changes immediately.

Edit CSS is available for download here.

10. Total Validator

The Total Validator Firefox extension provides one-click validation for HTML, Accessibility, Dead Links and more...

Total Validator is a complementary tool for standardistas out there.

I say "complementary" on purpose; because as you all know automated accessibility
checks don't mean much and the developer is responsible for passing each checkpoint manually.

BONUS

If have followed up to this point then you deserve a bonus don't you?

11. Noia Theme

Tired of the default Firefox look? Then install noia extreme theme. You'll be amazed how it changes look and feel of your Firefox.


... May the source be with you!

 bu yaziyi sevdin mi?  hemen una ekle!