I’d consider myself a Firefox “power user” – at one point I was pushing 50 extensions (I tried to keep it lean with my Macbook re-install, but still have managed to accrue almost 20). While I have a few extensions that have completely changed my browsing experience (SessionSaver, Adblock Plus + Filterset.G, Greasemonkey), these are extremely rare. I believe I’ve found three more today:

• SurfKeys – this defines a number of keyboard shortcuts for easier navigation
• Hit-a-Hint – this takes things one step further and creates a mode where every link element is numbered for instant keyboard navigation
• keyConfig – this is the same plugin that I discovered for Thunderbird and lets you re-assign all the keys for this and everything else in Mozilla to your heart’s content – every application should have this. I’ve changed my SurfKeys to a vim-like setup

(I’ve changed my HaH magickey to ‘H’ and disabled the rest)

The only thing I’m really missing from my browsing experience right now is slightly better live-editing of GM scripts/pages (Platypus is almost there) and radically better history/bookmarking (infinite caching of my page-content and browser/tab-paths/history please).