The list is probably based on the most rated Firefox extensions according to Download.com statistics.

1. FireFTP

FireFTP is a full-fledge FTP client for Windows. The extension is handy for developers who usually have to keep up and maintain their site using the File Transfer Protocol. FireFTP can handle multiple accounts and can even remember logins/passwords. It kills the need for an extra FTP client software.

2. DownThemAll

DownThemAll is a multi-download manager that makes it easy for you to download multiple link files from a given site or page. It auto-detects the downloadable links on a given web page and then allows you to download these files simultaneously or one by one

3. AdBlock Plus

PC World has rated AdBlock Plus as one of the best products of year 2007. This extension blocks advertisements and banners from a predefines list of ad providers.

4. Auto Copy

Auto Copy makes it easy for you to copy text from a web page. You can instantly copy a chunk of text by just highlighting it and it will be saved to the clipboard memory.

5. Better Gmail

Better Gmail compiles multiple Greasemonkey user scripts and brings you a fully-loaded high end Gmail interface. It integrates Google Reader to your Gmail inbox, offers search by date functionality, displays icons for attachments and offers cool new Gmail skins.

6. Gmail Space

Gmail Space is an ultimate need of all Gmail users which allows you to turn the 6GB big Gmail inbox into a file storage farm. Using this extension you can upload any sort of file to your Gmail inbox through a FTP-like interface and can later on download files from your Gmail storage box.

7. CustomizeGoogle

CustomizeGoogle will give you an enhanced and well customized Google Search interface which is free of ads and sponsored links plus it will show you search engine rankings for each result.

8. All-in-One Sidebar

All -in-One Sidebar is the only firefox extension that shall equip you with a sidebar in firefox (Just like in Opera). You can open and manage anything in your sidebar that you would not normally want to do in a Firefox tab e.g. manage downloads or view pop-ups.

9. Tab Mix Plus

Tab Mix Plus is the most adored Firefox extension that adds enhanced functionality to your Firefox tabs. With this extension you can use mouse gestures to control tabs, re-open closed tabs, duplicate tabs, merge tabs and much more.

10. Mr Tech’s Local Install

The primary goal of Mr Tech’s Local Install is to provide the tools needed to install and manage extensions and themes locally. To do this the extension provides multi-extension installation support, hacking capabilities to the Extension/Theme manager windows, features to find and troubleshoot Extensions/Themes Build, and Profile information.