If we look at the big picture view, most frequently people think of student contribution as code. But student learning can span HFOSS (Humanitarian Free and Open Source Software) as an item to be studied. You can draw artifacts from HFOSS and not contribute back, although that's not the preferred model. Contributing back starts the cycle of students being involved in a community. You can start as small as one assignment.
You can have students work as individuals or in teams, or even interacting teams. If you have a large number of students and you're going to have, say, five teams of four, you can designate a team lead for each and then have them interact. Deliverables can be anything from development artifacts to blog posts, code, podcasts, articles, etc. The sky is the limit. It doesn't have to be code.
Evaluation can be more than just submitted to the instructor. Submit it to the community and have them comment on and review it. Post or share it for peer review, present it in class. Think widely.
Beyond the code
Most HFOSS projects want contributions beyond the code and expect you to start small—quite likely outside the code. Try 50 Ways to be a FOSSer for ideas on other ways to get involved, from working on the business model to design and usability.
One good place for a class to start is with the history of a project. Have the students research the history of a FOSS project. They can read through listserv archives and IRC meeting logs to get a feel for the project before becoming involved.
Another option is to have students learn about communication processes for FOSS projects. Have them choose an RSS client and subscribe to relevant feeds, which they can read and summarize. They can then learn to use IRC, attending and summarizing meetings and learning to work remotely with one another. There are lessons to be learned in the social norms of communication within these communities.
How much you can change your curriculum varies from one place to another, and diving fully into a HFOSS participation course isn't always possible. In this case, start with small steps. Think in terms of a single assignment or an independent study. Have students participate in a research project or look for FOSS internships.
POSSE (Professor's Open Source Summer/Software Experience) is professional development for instructors interested in student participation in free and open source software. This post is based on a presentation at POSSE 2013 sessions by Heidi Ellis and Stoney Jackson of Western New England University.