Collaborative review tools help students actively engage with their peers in a course. Instructors can assign textbooks, articles, or PDFs, and students annotate these documents and respond to each other’s comments and questions.
A service called Tandem provides many review features for students (and instructors) to upload their own PDFs documents. Instead of reading a document and limiting discussions to the classroom, it brings the discussion to the text itself from anywhere. In addition, Tandem offers features like email alerts, filters, and analytics.