Experimental philosophy is the name for a recent movement whose participants use the methods of experimental psychology to probe the way people make judgments that bear on debates in philosophy.  Although the movement has a name, it includes a variety of projects driven by different interests, assumptions, and goals.  Just in the past few years philosophers have carried out experimental work in areas as diverse as epistemology, action theory, free will and moral responsibility, the philosophy of language, ethics, the philosophy of law, and the philosophy of science.   Given that "experimental philosophy" is perhaps best viewed as a family resemblance term, the boundaries are admittedly vague.  

But the following two questions nevertheless help shed light on what it means to be an experimental philosopher:  First, do you run controlled and systematic studies and use the resultant data to shed light on philosophical problems? Second, do you sometimes address the tension that exists between what philosophers say about intuition and human cognition, on the one hand, and what researchers are discovering about these things, on the other hand?  Experimental philosophy just is a movement at the cross-roads of psychology and philosophy that is being driven primarily by people who answer these two questions in the affirmative.