You will also have some to send to radio stations and club owners. Use these names to mail postcards with your show dates or CDs available. The cost to mail a postcard is cheap. The cost for e-mail is nothing. Build your own web page to list your shows and how to order your CDs.
Many services offer free or cheap home pages.
Maybe a newsletter, continious show updates, etc. You don't need to know how to program websites to have a guestbook. Use this as a template if you need a place to start. You can write these yourself. This costs practically nothing.