I've been working with Wiki Education for the last nine months researching student learning outcomes using Wikipedia based assignments. We have a ton of amazing data that we'll be posting about shortly and releasing under an open license (as well as a summary of some preliminary findings).
I've written a grant proposal for WMF to continue this research as we've really only touched the tip of the iceberg here. Please check it out and if you're interested I'd love your feedback (and your support).