Some libraries and schools will also be willing to take your name and card for reference and include you on a community list of providers. Another group to check to see if they maintain referral lists are local churches. Some may even allow you to leave business cards or post signs. Newspaper ads seem to vary in their effectiveness. They do cost a little money, but some providers have had good luck with them.
Many local papers are very interested in receiving story ideas profiling local citizens.
Some even will print a story that you write about yourself. This should not be an advertisement, but rather an informative article about the special things you provide your clients and unique aspects of your program. It is also much easier to get pictures into most newspapers these days than it has ever been. Just be sure that you have parental permission before trying to get children's pictures published. The phone book is also an option that sometimes is overlooked.