Google recently added a new feature to Gmail that allows you to create a new document in Google Docs with one click. As the GMail Blog explains:

No more copying and pasting the text from your email — just open the message you wish to convert, click the “Create a document” link on the right side of the page, and voila, you have a brand new document which you can then modify and share!

This feature is not turned on automatically. To turn it on, simply open your Gmail account, click on Settings, then click on Labs. Near the bottom is Create a Document. Click enable and then save the settings. While there, feel free to poke around the other options available and try them out if any catch your attention.

Hat tip to Reid Trautz for first pointing this out.