The WebLearn team is upgrading WebLearn to Sakai version 10 over the summer (2014). One of the great new features of the Assignments tool is that it allows peer review and grading (peer assessment). This screenshot shows two students who have each submitted an assignment, and each received one (anonymous) peer review with comments and a grade.
Note that the instructor needs to wait until the review period (specified when the assignment is created) is over, before checking the peer reviews and allocating a final mark:
See more details on this blog post from the University of North Carolina at Chapel Hill: