I have pledged allegiance to Google Docs. As a librarian graduate student, having an online collection base of my documents has opened up a whole new meeting to COLLABORATION. Case in point, we had this professor that gave a monster assignment (i.e. 30+ pages). We didn't know what to do, but yours truly figured her way out through the mud of it. So...as a true collaborator, I posted my entire findings on Google Documents to help my colleagues. The teamwork that ensued was amazing, because everyone could see my document from any location and add their feedback. In summary, it saved our skittles!
I can see using this as model for essay writing and ratings. I would love for students to read and leave comments on what they think this essay deserved (based on a state rating-rubric) for a score. The students could leave their justifications and then discuss it at their leisure. It will make for a great extension activity for them to do in support of the in-class instruction. The librarian can assist with the implementation of this Google Doc and Discussion Board.