A quick one for you via Digg: 20 Tips for More Efficient Google Searches – Dumb Little Man. I use some of these religiously, like the “site:” site search feature to search within a website, as Google’s site search is often better than the search capabilities offered by a site. I’m also partial to the calculator, as I use my Windows calculator much less because of it.
One other useful tip not mentioned here: if you use Google Desktop, double-tap the CTRL button and it will bring up a Google search box over your screen, whatever application you’re using. It’s often even quicker than using the Google Toolbar. If it doesn’t come up for you, turn on the feature in your settings.