Hi

Since Firefox has been in the news in few different posts, I am posting some extensions which have been used for a long time by me.  These are not hacker related extensions but useful for a safe browsing while taking the best out of FF. Somebody new to FF may find it useful.

If you are looking for hacker related extensions see the threads http://www.ethicalhacker.net/component/option,com_smf/Itemid,54/topic,1155.0/ or http://www.ethicalhacker.net/component/option,com_smf/Itemid,54/topic,1139.0/

Adblock Plus  (https://addons.mozilla.org/firefox/1865/)
Very useful  extension to block ad sites. U can customize this to allow ads from certain sites (white list).  Adblock Filterset.G Updater (https://addons.mozilla.org/firefox/1136/) is a companion to adblock plus but the folks at the adblock plus specifically tells not to use this extension as a companion to adblock plus as this may considerably slow down your browser. 

All-in-one Side Bar (https://addons.mozilla.org/firefox/1027/ )
Great tool to consolidate all the small tool windows in to a side bar. If u are a Opera fan you would love it. This tool simulates what opera does.  Lot of customization possible

Faster Fox  (https://addons.mozilla.org/firefox/1269/)
Tweaks some FF parameters to render/download pages fast.  U can do it manually in the config file, but you need to know the parameters you are looking at.

IE Tabs (https://addons.mozilla.org/firefox/1419/)
A must have for even Firefox die hards. Invariably u will come across sites which do not render properly in Firefox. With one click u can open a IE session on a FF tab. Also useful if u develop web pages.  Pages can be tested on both FF and IE with a click.

McAfee Site Advisor  ( http://www.siteadvisor.com/)
A useful tool if u enjoy downloading stuff. Once u install this every time u do a search from a search engine like yahoo or Google, it will add a icon to tell u whether the site is safe. Click on the icon and it will give more details of the site.

No Script (https://addons.mozilla.org/firefox/722/)
Disables JavaScript, Java and other executable content being executed automatically.  U can allow scripts only from websites you know to be safe.

Paste and Go (https://addons.mozilla.org/firefox/3035/)
Another dearly loved feature of Opera brought on to the FF platform. Paste and Go  lets you Paste Text and Load/Search It Immediately.  Search text box gives the additional option of “paste and search” and the URL box give the additional option “paste and go”

PDF Download (https://addons.mozilla.org/firefox/636/)
Extremely useful feature to stop the browser opening pdf file with the adobe plug-in. U control what u want to do when u click on a PDF link. Also I would advise u to try the free foxit pdf reader (http://www.foxitsoftware.com/) it is a single exe which loads incredibly fast. Rendering is not as good as Acrobat Reader but if u want to glace through a PDF and u want to load it quickly, this is the best.

Scrapbook (https://addons.mozilla.org/firefox/427/)
Save pages/websites and create collections on the hard disk. U can even add notes and delete sections u of pages u don’t need.

Tab Mix Plus (https://addons.mozilla.org/firefox/1122/)
Gives added functionality to the tabs.  Also includes a session manager.  FF 2 has a built in session manager but I have disabled it and still stuck to this.

CookieSwap (https://addons.mozilla.org/firefox/3255/)
Provides ability to maintains multiple profiles. Useful if u have multiple email account with the same site like Gmail or yahoo. Main drawback is the profile swap changes is browser wide NOT tab wide. This would be a great tool if it was possible to maintain different profiles in different tabs.

ImgLikeOpera (https://addons.mozilla.org/firefox/1672/)
As the name implies, another great Opera feature brought on to Firefox. But unfortunately this seems be broken after FF 2.

that on is also quite good- Down Them All!
https://addons.mozilla.org/en-US/firefox/addon/201