Firefox allows to conveniently add "keywords" to search boxes, to allow fast searching from its address bar.
For example, go to Google, right-click on the search box and select "Add a keyword for this search". Give it a name and a keyword, for example "g".
Now, you'll be able to just type "g whatever" at the address bar and Firefox will execute a Google search on "whatever" and show you the result. Combined with the Alt-D hotkey that places the keyboard cursor in the address bar, this is a nice productivity boon.
So far I've added keywords for Google, Wikipedia, Babylon (translations), and my own website (sometimes I look for stuff I've written on before).
Thanks to
Misha for the tip.
Eli Bendersky's website