Scholastic has a great service called Share What You're Reading that students can use to create and read book reviews online. Scholastic provides a simple form on which students can write and submit their book reviews. Students do not have to create an account to use the book review service.
Applications for Education
Scholastic's Share What You're Reading service is very easy for students to use and for teachers to incorporate into the classroom. The advantage of using the Scholastic service over a creating a wiki for the class is that the Scholastic service saves teachers time. The Scholastic service does not require users to create an account prior to writing a review. In fact, the only information they ever ask for is the student's first name, grade, and state.