Student PIRGs Open Textbook Reports - The student PIRGs has been a leader in research on textbooks for more than a decade, starting with the release of "Ripoff 101" in 2004. This link is to the chronological list of reports and research the Student PIRGs has published on textbooks.
Open Education Group Review Project - Conducts and publishes original research on costs, efficacy, and adoption of OER. Links to a bibliography of OER articles and dissertations auhored by researchers affiliated with the project. Primary researchers are Lane Fisher, John Hilton III, and David Wiley (all represented in the bibliography).