90 Firefox extensions

The ability to host extensions is one of the most powerful features of Firefox and one that makes it popular among users.  But which extensions should you install?  Which are the most useful?

I asked you, Firefox users, for your list of "must have" Firefox extensions.  From the comments you posted I extracted 90!

Have fun!

Don't blame me if this maxes out your Firefox install!  ;-)

Thanks to everyone who contributed to the list.