Here's a neat little OS X service that lets you search Google for terms you hilite in various applications.
From the web page: 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.
Pretty keen!
