Firefox Add-ons

I am always looking for ways to improve my Internet experience, and to that end I decided to share the list of Firefox add-ons that I use:

DownThemAll- download manager;
Foxmarks- bookmarks synchronizer;
Google Preview- inserts a picture of each webpage into Google or Yahoo search results;
Smart Bookmarks Bar- switches the bookmarks toolbar to icons only;
Tab Mix Plus- tab and tab options manager;
Ubiquity- see earlier post about Ubiquity.

Anyone have any great add-ons I am missing? I feel as if I do not see out new ones often enough, so I will be sharing any new ones I get as I come across them.