Though it's new, Realseekr.com features 1.6 million listings and is in the midst of aggregating hundreds of MLS databases into their website. Better yet, the listings are near real-time. No, I don't work for them. Yes, they will work for you.
On another front, have you considered Bluetooth marketing? That's right, the same thing that connects your phone to Bluetooth headsets can be used to freely send opt-in slideshows, videos and listing info to prospective buyers who pull up curbside. Unlike text message services, you don't need to know the prospect's phone numbers and it's free to receive Find out more about it at the website below.