Not sure if this would be Technician's Corner or Off-topic.
Fire fox is having a contest of the best extension and the Finalists
https://addons.mozilla.org/finalists.php
There are some ones I was not aware of and now hooked on a new one - Firefox Showcase by Josep del Rio. This is the "thumbnail" view of all pages (like the IE thumbnails).
The one thing I love about this extension, is if you have 2 instances of firefox windows, with say 3 tabs in each, when you use it it will show you all 6 thumbnails.
Firefox Extensions Contest - Finalists
EternalTempest