I love the ability to add comments to a student's document in Google Drive. Not only does it help students edit their work before a final submition, but it it is also a great way and give positive feedback at any time. I found the following video on FreeTech4Teachers.com and think it is the next step to commenting on a student's work directly from Google Drive. Teachers can add their own voice to a Google Document by adding an application from Learn.ly to their Google Drive account (see tutorial below). The following tutorial was made by Jennifer Roberts.