Tabbed browsing
gives you a better way to surf the net. You no longer have to open one page at a time. With tabbed browsing, open several pages at once with one click. And now your homepage can be multiple tabbed pages.

Popup blocker
lets you surf the web without intrusion. Advanced popup blocker notifies you when popups are blocked. You can also block pop-ups on a site per site basis.

Image Manager
lets you block images to block offensive images or to speed up the rendering of web sites.

Find as you type
gives you another way to navigate a page. Just start typing to jump from link to link or to find a word or phrase within a page.

Plus all the features a modern browser should have including: Advanced security settings; Password, Download, and Cookie managers;Themes; multi-language and multi-platform support; and, the latest in Web Standards. from offical site

Google Toolbar is the plug in wich instal into Mozilla Firefox Browser and help to discover internet sites . Here is screenshoot:

Google Suggests :Get query suggestions as you type in the search box.

SpellCheck :Check your spelling whenever you type in web forms.

AutoFill : Automatically fill out forms for faster online shopping.

WordTranslator : Translate English words into other languages.

Google Page Rank : PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual web page's value.

System requirements: • Windows XP/2000 SP3+, Mac OS X 10.2+, or Red Hat Linux 8.0+ ( from offical sites) A plugin (or plug-in) is a computer program that can, or must, interact with another program to provide a certain, Usually very specific, function. Plugins are slightly and different from extensions, which modify or add to existing functionality.
Browser plugins is wery useful tool for e-bussines people .
I have some good links thith mozila browser plugins ,