While speaking with a prospective client we learned that he promoted his Michigan printing business via the Detroit Chamber of Commerce.  Normally, this is a great opportunity to drum up some business, and their email list was well over 17,000 Detroit based business owners at the time of the broadcast email.  Thankfully, a mass email to their list only cost $85 at the time which is bargain basement cheap considering you are theoretically going to be targeting only business owners.