Now in Tiger, you can drag text directly onto an app's icon in the dock.
For instance, drag text onto Safari's dock icon, and Safari does a Google search with the string of text. Drag text onto TextEdit, and it opens the application and creates a new document with the dragged text. Drag onto Mail to create a new message with that text, etc.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050512222008166