Instead you'll want to target web sites serving the community you service, including Chamber of Commerces, newspapers, radio stations, television stations, and other local and regional businesses serving the same geography. Test, test, and test some more. Once you've got the perfect banner working, design another one because sooner or later even the best banner runs out of steam. It's generally accepted that after a prospect sees a banner for the third or fourth time, the likelihood of a click through plummets. When testing, always test the next new design on the same site or on the same network, so you are indeed comparing apples to apples.
Testing is a continual ongoing, dynamic process.
Review your stat pages on a daily basis and be prepared to act quickly when results begin to lag. Remember the three most critical elements of your banner. First the copy, next the color, and next the graphics.