Free marketing is always the best kind!
With haunts I have worked with in the past we have done several parades and festivals which are almost always completely free to enter, you just need to get ahold of the city's Chamber of Commerce for registration. With these most of the time are hitting your core audiences. You might want to have some promo materials on hand to pass out, but showing off your characters and what they can expect coming to your attraction is 100% free. Many large concert venues will also allow you to flyer inside as well as outside the door with permission. We had great responses for both advertising the haunts as well as recruiting some new actors with all of these methods. You can also often get free spots on college radio stations...utilize any connections you have, there are a lot of creative and free ways to get your name out there.
Mike "Pogo" Hach