I will not use firefox without these. I used these while developing my site Friv
Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
Google translate gadget for firefox. This extension translates entire webpages into a language of your choice with one click. Idea comes from Google Translation Bar for Chrome.
Collections are groups of related add-ons that anyone can create and share.Explore Collections