here are a few firefox shortcuts that i find really handy:
everyone (hopefully!) knows that [ctrl*] and [tab] switches between the tabs ([ctrl] [shift] [tab] works through the tabs in the opposite direction). but using [ctrl] and a digit-key  –  lets you directly access a certain tab without having to go through all the tabs between the active and desired tab.
[f6] isn’t really an insider’s tip, but i’m sure a lot of users don’t know you can jump to the address field. alternatively you can use [ctrl] [L].
you can reach the built-in search field in your navigation bar by pressing [f6] and [tab]. another (easier) option is to use [ctrl] [K].
the search-engine can be changed pressing [ctrl] [Up] and [ctrl] [Down].
* [ctrl] (“control”) is called [strg] (“steuerung”) on german keyboards, just in case you start searching desperately :wink:
for a complete list, visit www.mozilla.org/support/firefox/keyboard.