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).
Collector's Note I highly recommend the EasyList, EasyPrivacy, and AntiSocial filter sets.
Status bar widgets and progress indicators for Firefox 4+
DOM Inspector is a tool that can be used to inspect and edit the live DOM of any web document or XUL application. The DOM can be navigated using a two-paned window displaying a variety of different views on the document and all nodes within.
Collections are groups of related add-ons that anyone can create and share.Explore Collections