(Update) My Favorite Firefox Extensions - Part 2

In No Particular Order

Adblock - Once installed, it’s a snap to filter elements at their source-address.
Just right-click: Adblock: done. Filters use either the wildcard character (*)
or full Regular Expression syntax. Hit the status-element and see what has or
hasn’t been blocked.

DictionarySearch - Looks up a user selected word in an online dictionary

Google Preview - Inserts preview images (thumbnails) of web sites and Amazon products into the Google and Yahoo search results pages.

BugMeNot - Bypass compulsory web registration via Firefox’s right-click context menu. Compatibile with Mozilla and current Firefox releases. Visit bugmenot.com for full details of their service.

StumbleUpon - StumbleUpon lets you “channelsurf” the best-reviewed sites on the web. It is a collaborative surfing tool for finding and sharing great sites. This helps you find interesting webpages you wouldn’t think to search for.

VideoDownloader - Download videos from Youtube, Google, Metacafe, iFilm, Dailymotion… and other 60+ video sites ! And all embedded objects on a webpage (movies, mp3s, flash, quicktime, etc) ! Directly !

Tab History - TabHistory provides two histories of the tabs.

The first history is automatic. Whenever you change tab, the tab you change to will be added to this history. To go back to the previous tab, press Ctrl+, (Ctrl+comma). To go to the next tab in the history, press Ctrl+. (Ctrl+dot).

The second history is manual. To add a tab to this history press Ctrl+Shift+M (think "mark tab"). To go back to the previous tab in this history press Ctrl+Shift+, and to go to the next tab in this history press Ctrl+Shift+.

This saves you from the situation of having many many tabs open and not being able to remember which one you were previously at and thus having to spend ages searching through all your open tabs.

Tab Effect - Add effects when current tab is changed. this extension uses DirectX 8.

Sage - Sage is a lightweight RSS and Atom feed aggregator extension for Mozilla Firefox. It’s got a lot of what you need and not much of what you don’t.

Super DragAndGo - Drag a link or anything like a uri (e.g. "abc.com" ), and throw it to anywhere blank on the webpage to open the it in a new tab.

Colorful Tabs - The most beautiful yet the simplest add-on that makes a strong colorful appeal. Colors every tab in a different color and makes them easy to distinguish while beautifying the overall appearance of the interface. An essential.

IE Tab - IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox.

FireFTP - FireFTP is a free, secure, cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers.

Along with transferring your files quickly and efficiently, FireFTP also includes more advanced features such as: directory comparison, syncing directories while navigating, SSL encryption, file hashing, and much more!

GreaseMonkey - Allows you to customize the way a webpage displays using small bits of JavaScript.
Hundreds of scripts, for a wide variety of poular sites, are already available at http://userscripts.org.
You can write your own scripts, too. Mark Pilgrim’s definitive Greasemonkey guide, diveintogreasemonkey.org will show you how.

Image Zoom - Easily zoom in, zoom out, fit image to screen or set custom zoom on individual images within a web page. All this can be done by using the context menu or a combination of mouse buttons and scroll wheel. Handy to see the finer details of smaller pics or to make very large pics fit within your screen.

Auto Copy - Select text and it’s automaticaly copied to the clipboard. Like Linux or mIrc.

gTranslate - With gTranslate you can translate any text in a webpage just by selecting and right-clicking over it. The extension uses the Google translation services to translate the text.
gTranslate is not affiliated with Google Inc. in any way.

Foxmarks - If you use Firefox on more than one computer, you’ll want Foxmarks. Install Foxmarks on each computer, and it will work silently in the background to keep your bookmarks synchronized. As a bonus, log in to my.foxmarks.com from any computer anywhere to access your bookmarks.

A simple wizard guides you through the startup process. After that, just forget about it. It’s simple and solid.

URL Fixer

URL Fixer is an extension for Mozilla-based Web browsers that corrects typos in URLs that you enter in the address bar. For example, if you type google.con, it will correct it to google.com (asking first, if you enable confirmation).

Speed Dial

Speed Dial allows fast access to your most visited websites. It loads in a tab, and will show thumbnail views of it’s assigned websites. Those thumbnails will be refreshed automatically in the background.

Firefox Showcase

Showcase provides a new way to manage your Firefox tabs and windows by showing them as thumbnails in a single window, tab or sidebar. Includes a find bar that will filter the thumbnails, and the capability to select the thumbnails in the same way you would select files in your system.

Zotero

Zotero is a free, easy-to-use Firefox extension to help you collect, manage, and cite your research sources. It lives right where you do your work — in the web browser itself.

PicLens

PicLens instantly transforms your browser into a full-screen, 3D experience for viewing images on the web. Photos will come to life via a cinematic presentation that goes well beyond the confines of the traditional browser window. With PicLens, browsing and viewing images on the web will never be the same again.
NEW! Immerse yourself in 3D Style.

I will add to this list when I find more my favorite Firefox Extensions.