There are any number of ethical questions you could research from the standpoint of how various religious beliefs have or will take a position in answering the questions. Examine what one or more religions believe and teach in looking at genetic design, cloning, homosexuality, the death penalty, the moral ramifications of military actions, etc...
You could also research the origins of specific religions. I find it interesting to see how various groups began and broke off from one another. For instance, the Lutherans and Protestants breaking away from the Catholic church. The origins of the Mormons and Scientologist are also quite interesting. The climate of the period when a religious group formed has a profound effect on that religion. It is interesting to look at how different groups formed at different time periods. It is interesting to see how each sect changes as they move further from the period they were created in.
An interesting area of research in religion is the role of the woman in various religions, historically and today. How in the world did it happen that many of today's major religions place women in a lesser role? As a subset of that topic, there has been extensive research done on a group of nuns, published maybe ten years ago. This was a health study, but an interesting example of how a religious life can influence us in many ways. Another prospect for research is some recent interest in the connection between religious experience and our brain chemistry. Yet another area which might be of interest is what religious actually is. How do we distinguish between a religion and a cult? Can a cult become a religion? In today's political climate, there are any number of interesting ways in which politics and religion mix, with Mormon candidates and an Islam Center near Ground Zero, people burning the Qur'an, and so on.
It seems to me that research in religion must focus on some tangible aspect of it, for example, sociology, psychology, or history, since religion is, by definition, a matter of belief, and no research in the world will ever establish the "truth" of a religion or the lack thereof.
The most interesting question in philosophy of religion is whether human beings are all reaching towards an actual truth that is out there or whether all religions are simply manifestations of us fooling ourselves and hoping that our existence will not end when we die. Of course, this (and most questions about religion) are not really researchable.
As far as something researchable, perhaps you could look at the degree to which religious beliefs are determined by the circumstances in which they arose. That is, is there something about the time and place that Islam (for example) arose that had an impact on its messages and beliefs?