I use a varitiy of add-ons, some that have been mentioned (IE Tab, DownThemAll) but one add-on I don't think I could live without is Foxmarks ( http://www.foxmarks.com/ ). I have five computers in my room, and the ability to have them all have the SAME bookmarks saves me the trouble. I can also just login online to their server and find my book mark when I'm away from one of my computers.
Those of you into web building and such, I also use
Flagfox ( displays what country the server is located and gives detailed information on it. )
JSVIEW ( Javascript code viewer )
URL Fixer ( Fixes .cmo to .com, does not always work for small issues though. )
And I use to use Cooliris at one point, allows you to view a site by just hovering over the link.
I see nobody mentioned the Remove It Permanently add-on which IMHO shouldn't lack in a Firefox installation
I also recommend these two add-on PopupMaster or Yes Popups because even though firefox comes with it's own block popup option, sometime some popup are able to evade that.
Ah, and another fun add-on is Persona. It's like themes except without the fancy button change.
Grease monkey
Grease monkey is usefull for some sites, it allows custom scripts to be runned(Java if I remember correct) and example add features to youtube or automate some boring tasks.
Hmm I recommend to use
Fastest Fox
It's make easier in reading manga because we can scroll the page 'till one chapter of manga (this just can be used at Mangafox). and it give other feature like giving website links, etc.
Inline Translator
for translating other language, by block the word that you want to translate, it's easy to use. There are many language that available to translate like Arabic, Bulgarian, Catalan, Chinese, Croatian, Czech, Dutch, English, Japanese, Korean, etc.
FireShot
FireShot is a Firefox extension that creates screenshots of web pages (entirely or just visible part).
Unlike other extensions, this plugin provides a set of editing and annotation tools, which let users quickly modify web captures and insert text annotations and graphical annotations. Such functionality will be especially useful for web designers, testers and content reviewers.
Just a heads up on this add-on. I've recently found that this add-on severely bogs down Firefox when browsing this forum. I'm running Firefox on a Mac, and don't know if this is the case with the Windows platform (could someone with this add-on confirm this?), but something to keep in mind.
If you normally use a lot of tabs and worry about firefox using too much memory because of that, Bartab might be the add on to check out. You can set the options to where it automatically doesn't load home tabs until you click on them, and they will still be in the background, just not eating up a lot of memory. Its worth a try at least if you have problems with firefox and memory usage, or if you use many tabs at once.
I recommend Better Privacy
https://addons.mozilla.org/en-US/fir...betterprivacy/
"Better Privacy serves to protect against not deletable longterm cookies, a new generation of 'Super-Cookie', which silently conquered the internet. This new cookie generation offers unlimited user tracking to industry and market research. Concerning privacy Flash- and DOM Storage objects are most critical.
This addon was made to make users aware of those hidden, never expiring objects and to offer an easy way to get rid of them - since browsers are unable to do that for you."