Firefox extensions

The question has been asked alot of times but what are THE top Firefox extensions? As I just discovered Session Saver I want to share it with everyone :-) The thing does what it says: if you close Firefox it saves the session as is (tabs and the like). This is really handy as I don't have to save bookmarks I don't really want to keep just to know where I left.

As we are at it, here are other extensions I really couldn't live without (as a figure of speech of course):

Adblock and Adblock Filterset G. They block almost every ad. Need I say more?
Del.icio.us. As I am a big del.icio.us fan, this one is a must have.
IE view. This extensions opens a page in IE instead of Firefox if needed.
Dict looks up words in the dictionary and opens in a new window.
Greasemonkey. This one allows you to apply transformations to websites dynamically and much more. Just click the link and find out for yourself.

I am sure you guys use many more I haven't heard of so don't hesitate to post (yeah you my 2 readers and a half)