Here is a link (PDF) to my research paper on "Designing an Educational Alternate Reality Game," which contains a good set of 40+ references to other related papers and articles in the bibliography: http://www.shoyu.com/education/Research_DesigningAnEducationalARG.pdf
Also, this annotated bibliography has a lot of good educational ARG research resources: http://remotedevice.net/blog/arg-readings-and-reflections-an-annotated-bibliography/.
--Randall