Remember the Quick Search powertoy for IE? Well, now it's built in. Load up TweakUI and expand the Internet Explorer menu. Under search, you can create new search options. For example:
Create one with a prefix of "g" and a URL of "http://www.google.com/search?q=%s". Now, to search Google for, say, penguins, all you have to do is type "g penguins" in the Address bar. Nice and easy.