Ever collaborated with Google Docs? By now everyone should know how to share a Google Doc & work with others on the same doc or spreadsheet. But how about for peer-editing or student/teacher feedback? Google Docs has a robust revision history and powerful commenting tools built-in to take the collaboration experience beyond just typing in the same doc.
Text-specific comments: Simply select some text, right-click and choose 'comment'. This will let you add personal comments associated with the text.
Document-wide comments: Click on the Comments button in the top right corner. You can add comments that aren't just specific to individual slices of text. You'll also see the running chain of all the comments & replies, as well as who sent them.
Resolve comments: Click on any given comment and you can click the 'resolve' button. This will hide it from the main page view, so you can move on to the next comment.
Notification settings: Choose to be emailed when people comment on your document, or if they reply or even mention your name. No need to check-in every hour to see if people have provided you feedback yet.
Revision History: See everything anyone's ever changed in the document, in a clear color-coded manner. Just click File -> See revision history.
Restore version: From the revision history you can even go back to a previous version and start again. Just click on the version on the right and choose Restore this revision.