My dojo has also experienced the same trouble. People move to new towns, students go away to college, etc. I was even one of the students (assistant instructor) who had to leave eventually. When I relocated (I'm in the US Air Force) I wanted to spread the joy of Aikido to others so I went to the local Youth Activities Center and did some paperwork to begin teaching classes on the base. Advertising for my classes was easy, the center sent out a base-all e-mail. It didn't work very well though. You are right, not many people have heard of Aikido. I took it upon myself to advertise by placing information about the class in the buildings around town and on the base. I also posted information about a question/answer session and demonstration about Aikido principles. If your dojo is located near a college or university, it wouldn't hurt to post some advertising signs on campus. Check with local stores and ask if they have a bulletin board that is used to give information about local activities. These are just some ideas, some may work for you and some may not. I wish you good luck in your quest for students.