FYI, deleting AddBlock Popup as it sucks, thinking ditching xmarks since Firefox can sync now.
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).
The first and only download manager/accelerator built inside Firefox!
Find out which websites you can trust. WOT adds intuitive traffic light-style icons next to search results and URLs to help you make informed decisions about whether to visit a site or not.
Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.
Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
Collector's Note This may get smoked as Firefox can sync solo, no cross browser syncing thought, but I only book mark in FF anyway... Thoughts?
Browse faster—Preview links and images without leaving your current page or tab. Just mouseover any link and a preview window appears to display the content.
3D in your browser! FoxTab brings innovative 3D functionality to your Firefox.
New! Top Sites for FoxTab (aka Speed Dial).
With this extension you can quickly paste any type of text to the website http://pastebin.com
Leading dictionary lookup add-on. Fast, light, open source tool that define words for you without need to open new tabs or windows. Wiktionary&Wikipedia.
Ctrl or Shift or Alt + RightMouseButton click. Now with thesaurus.
70+ languages supported!