Google Docs is great for collaboration. Teachers can comment on student assignments and provide individual feedback.

The challenge: 10 comments per student x 100 students = 1000 email notifications!

The solution: Turn off comment notifications!

Just don't forget to warn your students, you will not see when they respond to or resolve comments. They will need another way to tell you if they want you to revisit their paper. They could try File--> Email Collaborators.