Having said that, however, I spend most of my day on the internet working for the haunted attraction industry, so I do have some thoughts and insights on the subject, which follow.
First, and most importantly: There is no one place you can buy an ad or featured listing that is guaranteed to work for you - different markets and geographic locations get different results from the same websites. National-level haunted house finder sites may work well in some areas, but will rank behind localized haunt finder sites in others. Take HauntedHouseChicago.com, for instance - do a search on Google or Yahoo! for pretty much any combination of the words "haunted" "house" and "Chicago", and HauntedHouseChicago.com will be the first link you see - national-level haunted house finder sites don't even rank in the first 10 results.
Obviously, not every market has a site like HauntedHouseChicago.com; many of them rely on the national-level sites for their internet traffic, and so should avail themselves of those sites.
Probably the best way to determine where you should focus your online advertising dollars is to do some test searches on Google.com and Yahoo.com. Put yourself in the headspace of the people that you want to find you online - you want people who (a) want to go to a local haunted house and (b) DO NOT already know about yours*. What words would they use to search for haunted houses in their (your) area? Do those searches yourself and see what websites come up in the top five results - those are probably where you should be buying your featured listings and ads.
Also, if you aren't using FREE sites like Facebook, Twitter, MySpace and other social networking sites to promote your haunt, you're behind the curve - but I've already covered that in a previous post.
*When it comes to featured listings and ads, the name of the game is NEW customers - don't worry about the people who already know about your haunted house. They'll find you. Focus on the people who DON'T know about your haunted house - that's where you'll maximize your ad budget.