Select some text. Hit “Shift-Apple-G”. Get Google results:
Search Google – A simple background service to allow you to select text in (nearly) any application and press “Shift-Apple-G” to launch a Google search for that text. This release is context aware. When you select text from Project Builder, a browser opens up searching developer.apple.com instead of Google. You can define your own contexts (application-grain) and choose what URLs they apply to.
GooSearch is another Google search tool that is available for Mac OS 9 and X.
