Do you find yourself replying to the same messages repeatedly? The days of typing or copying and pasting similar responses by hand are over.
Gmail recently introduced "canned responses" to their labs. This new feature allows you to have pre-defined e-mail responses ready to go. Instead of spending time replying to all the inquires that you get on your business e-mail for example, you can select from predefined responses.
Check out some more information at gmail's blog. http://gmailblog.blogspot.com/2008/10/new-in-labs-canned-responses.html