We all know there are hundreds of firefox extensions and more are released with every passing day. It´s a time consuming task to stay up to date, that´s when pre compiled lists of useful firefox extensions come into play. This one at cerias (The Center for Education and Research in Information Assurance and Security) lists firefox security extensions that are security related.
The author lists 11 extensions, some known ones like LiveHttpHeaders and NoScript and lots of unheard ones like formfox. Each extension is explained in detail and linked to the mozilla website for more information and downloading.

Problematic Firefox Extensions
Firefox Catalog of Auditing Extensions FireCat
5 Essential Firefox Extensions
Increase Firefox Security With FormFox
Firefox Extensions Website Gets Overhaul. Collections Introduced