The real estate vertical is one of the most interesting online segments for several reasons. Among them are the tools that have been developed amid intensifying competition.
Mapvine is a free tool that enables anyone to place map-based listings (rentals, store locations, etc.) on their sites without any technical knowledge or expertise.
Rentometer allows you to compare what you're paying to average rents in your area. For example, before my wife and I moved from San Francisco, CA to where we live currently we were paying approximately $1375 a month in rent (over four years ago). Today that looks like an incredible deal.
Rentometer also shows you the highest rents by zip and by city.