- Adblock Plus - Bye bye annoying advertisements!
- AutoPager - Tired of clicking around? AutoPager might help in this. It allows you to browse next pages of many popular sites just by loading them on the current page automatically.
- Flashblock - Adblock for Flash. Nuff' said.
- Greasemonkey - Greasemonkey allows you to extend web pages locally. In case you don't feel like writing extensions on your own, you might find a few at http://userscripts.org/.
- Web Developer - A definite add-on for a web developer.
- Zotero - If you do any research you might find Zotero extremely handy.
- Omnibar - Combines search with location bar just like in Google Chrome
I thought it might be nice to hide the menubar of Firefox. With a bit of poking around I managed to find Hide Menubar that does the trick. Should you wish to see the menubar again, just hit alt. :)