Here is a Collection the top 20 firefox add-ons..

Add-ons:-

1.)Adblock Plus
https://addons.mozilla.org/en-US/firefox/addon/1865

2.)Firefox Showcase
https://addons.mozilla.org/en-US/firefox/addon/1810

3.)Foxmarks Bookmark Synchronizer
https://addons.mozilla.org/en-US/firefox/addon/2410

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4.)CookieCuller
https://addons.mozilla.org/en-US/firefox/addon/82

5.)CustomizeGoogle
https://addons.mozilla.org/en-US/firefox/addon/743

6.)Fullerscreen
https://addons.mozilla.org/en-US/firefox/addon/4650

7.)GButts
https://addons.mozilla.org/en-US/firefox/addon/3576

8.)GMail Manager
https://addons.mozilla.org/en-US/firefox/addon/1320

9.)McAfee SiteAdvisor
http://www.siteadvisor.com/download/ff.html

10.)Restart Firefox
https://addons.mozilla.org/en-US/firefox/addon/1249

11.)Screengrab
https://addons.mozilla.org/en-US/firefox/addon/1146

12.)Session Manager
https://addons.mozilla.org/en-US/firefox/addon/2324

13.)StumbleUpon
https://addons.mozilla.org/en-US/firefox/addon/138

14.)Tab Mix Plus
https://addons.mozilla.org/en-US/firefox/addon/1122

15.)Toolbar Buttons
https://addons.mozilla.org/en-US/firefox/addon/2377

16.)Translator
https://addons.mozilla.org/en-US/firefox/addon/3361

17.)WHOIS
https://addons.mozilla.org/en-US/firefox/addon/603

18.)Google Bookmarks Button
https://addons.mozilla.org/en-US/firefox/addon/2453

19.)IE Tab
https://addons.mozilla.org/en-US/firefox/addon/1419

20.)Yahoo! Mail Notifier
https://addons.mozilla.org/en-US/firefox/addon/1264

Read more: http://www.earnmoneyfromblogs.co.cc/2011/01/top-20-add-ons-for-firefox.html#ixzz1D1r8zMK3