I like the idea that you have access to all of your revisions. Too often students revised something and it is not really better. They might want to go back to the original one but they do not have it saved. This way they can go back and see the progress they have made. It is also an easy way for others to help with editing.
This website has many different parts. It includes "34 Ways to Use Google Docs in the Classroom", "34 Ways to Use Twitter in the Classroom," "70 Ways to Use Google Forms in the Classroom" There are also many more online and offline activities.