Why firefox 10.1 uses full screen on Snow Leopard while Chrome and Safari do not?
I love Divvy - it's something that I feel OSX needs and that would allow you to set a shortcut for it. Otherwise the green orb on the top left will take you to full height, and then you can drag out horizontally to your chosen width. 

Alternatively, should you upgrade to Lion, Chrome has a full-screen mode which hides all the other apps.