Many time you have a good conversation on gmail and later you thought to put all these things in a single document. Jeremie Lenfant-Engelmann, a Software Engineer at Google released the same. The information contained in the messages would make a great starting point for a document. So he built an experimental feature for Gmail Labs that does just that: with one simple click, "Create a document" converts an email into a Google Docs document.
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!
Even if you're not interested in converting any of your current messages into documents, you can easily open up a blank doc by hitting g and then w (just make sure you have keyboard shortcuts on).
To turn on this feature, go to the Gmail Labs tab under Settings, select "Enable" next to "Create a document" and hit "Save Changes" at the bottom.