Firefox

shortcut	Description
alt+d or ctrl+l	Jump to address bar
ctrl+k	Jumps to search bar if installed (ctrl+e used to do so as well, but seems to be discontinued)
tab/shift+tab	Jump to next / jump to previous link
shift+ctrl+enter	Open selected link in new foreground tab
ctrl+enter	Open selected link in new background tab
shift+enter	Open selected link in new window
f7	Turn caret mode on or off (navigation with keyboard)
ctrl+u	Show page source
ctrl+j	Open or close download window

Source: http://www.shortcutworld.com/en/win/Firefox_6.html