I have actually thought about having a customer appreciation at a local private club. Just renting it out for a few hours on a Thursday or Friday evening (right after work) for a cocktail house. 

I rented out a movie theater in a past job.  It really isn't THAT expensive but it was hard to get people to show.  I would suggest a family type movie to inspire people to bring their kids. 

If you want business people/after hours crowds, places like Jillians, Dave and Busters, Boomers often have special party rates - they throw in a couple of appetizer trays and everyone picks up their own bar tabs.

If you're farming a particular neighborhood, you could ask about using their clubhouse.  Theme it too.  Rent a projector and show some kid movies and have some teenagers there to babysit and have facepainting, balloons etc.  You could call all the listings and do a caravan.  You may even be able to arrange for one of those tractors with the trolley car on the back like they use at fairs to literally bring everyone at once.  Get the local high school cheerleaders/girls softball to be greeters/hostesses for you at the different houses and have them hand out nice flyers.  Make it a "Progressive" lunch/dinner with different foods at every stop.  Maybe Tapas?  Have the high school baseball team wash cars too... let parents donate to them for babysitting and car washing and let them keep the proceeds to benefit uniforms or a travel game.  If you build enough momentum (this would be great to schedule for Spring)... you could definitely build some interest and if you're organizing you should be able to be in the forefront for all the new listings!  Send out PLENTY of reminder cards and flyers.

This will also expose you to all the FSBOs and other agents!  Get them in on it and in on the cost!