No matter what you make or sell ( with very few exceptions) the military is likely a buyer. They love to do business with small business but you have to approach it correctly. One of the ways to do this is to go to www.sba.gov and search for doing business with the military.
Here is a great website to help you through the process, http://www.defense.gov/landing/contract_resources.aspx. This is the site for the U.S. Department of Defense which deals with all branches of the military. The only exception here would be the U.S. Coast Guard. Go to http://www.uscg.mil/acquisition/business/business.asp because the Coast Guard is controlled by the U.S. Homeland Security Administration.