NoScript, possibly the best thing about FF. Firebug, pretty handy. Tamper Data, for viewing HTTP headers and tampering with them. ShowIP, shows the current w

NoScript, possibly the best thing about FF. Firebug, pretty handy. Tamper Data, for viewing HTTP headers and tampering with them. ShowIP, shows the current website's IP. leetkey, great for text transformations, various encoders/decoders. Screengrab, for taking screenshots. Scrapbook Plus, for archiving pages (can also do some light crawling with it) Mozilla Archive Format, also for archiving pages. Delicious Bookmarks, for bookmarks. AppTab, to make tabs sticky. OptimizeGoogle, to make Google searching better. UnPlug, for downloading embedded content. DownThemAll, for downloading things. HTTPS-Everywhere, redirects to HTTPS versions of certain websites. ErrorZilla Plus, makes error pages more useful. Those are the best ones, I use various other extensions depending on what I'm doing. I have a few addons deactivated at any given time.