1.) PDF Download
This is an excellent addon for converting and downloading web pages in to PDF by a single click!
https://addons.mozilla.org/en-US/firefox/addon/636
2.) Nodofollow
This addon Highlights links in web pages according to their dofollow / nofollow status. This is a highly recommended addon for webmasters for seo.
https://addons.mozilla.org/en-US/firefox/addon/5687
3.) Search status
This addon displays Google PageRank, Alexa rank, Compete ranking and SEOmoz Linkscape mozRank with lots of seo tools.
https://addons.mozilla.org/firefox/addon/321
4.) Un plug
This addon saves embedded videos and audios with a single click. Its a brilliant addon and i highly recommended it. This addon compitable with Downthemall.
https://addons.mozilla.org/en-US/firefox/addon/2254
5.) Read It Later
Read It Later allows you to save pages of interest to read later. It eliminates cluttering of bookmarks with sites that are merely of a one-time interest.
https://addons.mozilla.org/en-US/firefox/addon/7661
6.) FireFTP
FireFTP is a free, secure, cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers.
https://addons.mozilla.org/en-US/firefox/addon/684
7.)FoxyProxy
Foxproxy addons remove the limitations of traditional limitations of proxy settings of firefox browser
https://addons.mozilla.org/en-US/firefox/addon/2464
8.) Downthemall
The first and only download manager/accelerator built inside Firefox. Its a brilliant addon which really speed up downloading speed up to optimum level.
https://addons.mozilla.org/firefox/addon/201
9.) Fox tab
FoxTab brings innovative 3D functionality to your Firefox. FoxTab is a 3D tabbed browsing extension. With 6 attractive layouts to choose from, flipping between opened tabs becomes both easy and fun.
https://addons.mozilla.org/en-US/firefox/addon/8879
10.) FEBE
This addon is used for making back up of firefox addons. It saves firefox addons as .xpi file.
https://addons.mozilla.org/en-US/firefox/addon/2109