You most certainly can. During the most recent refinancing boom, for example, many homeowners refinanced their home loans two or three times within relatively short periods of time because interest rates kept treading downward, making it extremely attractive to trade in one loan for another.
Just remember that refinancing is basically like applying for a mortgage all over again. Each time you refinance, you will still have to go through the application process, get a home appraisal, and likely incur closing costs. Also, if you have a pre-payment penalty clause in your present mortgage, you will have to pay that penalty if you refinance. So be certain that it is actually worth it for you to refinance.