I gave an interesting assignment last semester that asked students to complete their research paper as an article on Wikipedia. My course was recently profiled on the Wikimedia Foundation blog.
Of particular note, the article covers my reflections on the way working on Wikipedia changes students relationship to power, forces/inspires them to do real research, inspires them to work for the greater good, and curtails/moderates plagiarism.
I will be trying a shorter version of the assignment with the Core 2 seminar in the Interactive Technology and Pedagogy Certificate Program at the Grad Center. More on that as it develops.