This is a crib sheet of firefox key bindings.
These are the key bindings I use most often.

[S] = Shift
[C] = Ctrl (Cmd for Mac)
[A] = Alt
DEFAULTS
-----------
A list of defaults is available here.

[S]-LCLICK	Open link in a new window
MCLICK or	Open link in new bgrnd tab
[C]-LCLICK

[S]-MCLICK or	Open link in new fgrnd tab
[S]-[C]-LCLICK

[A]-LEFT/RIGHT	Back/Forward
or
[S]-SCRL-DN/UP

[C]-=		Make text larger
[C]--		Make text smaller
[C]-0 (zero)	Return text to default size
[C]-SCRL-DN/UP	Make text larger/smaller

[C]-D		Bookmark current page
[C]-B		Open/close Bookmarks sidebar
[C]-H		Open History panel in sidebar
[C]-Y		Downloads ([C]-J Windows/Mac)

[C]-T		Open new tab, focus to URL bar
[C]-W		Close tab
[A]-1->9	Go to tab number 1->9

[C]-L		Goes to the location bar, 
		highlights the current address 
		so that I can copy it, paste 
		over it, or just start typing.
[C]-ENTER	When focus is in location bar, 
		opens URL typed in location bar 
		in a new tab.

[C]-K		Go to search box
[C]-UP/DN	Toggle search engines when 
		focus is in search bar.
[A]-ENTER	When focus is in search bar, 
		opens search results in new tab.

[C]-I		Page info

[C]-F		Find in page

[C]-U		View source

[C]-A		Select all

[C]-N		New window
[C]-[S]-W	Close window

[C]-O		Open file

[C]-P		Print

[F5]		Reload
[F11]		Full screen

/               Find text as you type
'               Find link as you type
CUSTOMIZED
-------------
Set via particular extensions or with the 
Keyconfig extension

[C]-[S]-[F12]	Keyconfig

[S]-LEFT	Previous tab
[S]-RIGHT	Next tab

[C]-S		Find next
[C]-R		Find previous

[A]-S		Save as
[A]-R		Refresh

[A]-I		Manage bookmarks

[C]-Q		Close tab, focus to left
[C]-[F12]	Undo close tab
[C]-[S]-T	Duplicate tab in new tab
[C]-[S]-N	Duplicate tab in new window
[C]-[S]-M	Merge tabs from this window
		with all tabs from window
		last opened and kill 
		current window.

[C]-[S]-	On search pages with multiple 
LEFT/RIGHT/	pages of results, go to 
UP/DN		previous/next/first/last page.

[C]-1->9	On search pages with multiple 
		pages of results, go to page 
		number 1->9.

[A]-O		Preferences

[A]-[S]-C	Open calculator

[A]-[C]-C	Capture a portion of a URL
		to in(de)crement

[C]-DBL-CLICK	Defines word in a tooltip

[C]-[S]-S	Customize menus

[A]-[S]-E	Extensions

[C]-[F11]	Toggle Stumbleupon toolbar
[A]-[C]-S	Stumbleupon Stumble!

[A]-[C]-R	Restart

[C]-[F1]	Save this window

[F8]		Toggle tab slideshow
[F9]		Toggle tabs focus to right or
		last-viewed

[A]-C		about:config
[A]-P		about:plugins
----------------------------

A wicked quick way to search for something...
Highlight it -> [C]-C -> [C]-J -> [C]-V - [A]-ENTER

A wicked quick way to load a text URL...
Highlight it -> [C]-C -> [C]-L -> [C]-V - ENTER