.com - Type the Url without the .com then hit Ctrl + Enter.
.net - Type the Url without the .net then hit Shift + Enter.
.org - Type the Url without the .org then hit Ctrl + Shift + Enter.
Those are the main ones that are used and can really help getting you to where you need to be faster without having to type as much. Also if you do not have Firefox installed you can get it here: www.firefox.com.