Real estate professionals have a growing choice of businesses that offer API keys to enhance their Web sites.
While many offer tools and data free in exchange for branding, some charge fees for an annual subscription or for specific levels of usage.
For more about the services, requirements and conditions of some of the most popular APIs, visit these sites. Market research and analysis Zillow www.zillow.com/howto/api/ APIOverview.htm
Trulia http://developer.trulia.com RealtyTrac Foreclosure Listings www.realtytrac.com Mapping Google Maps http://code.google.com/apis/maps Mapquest http://developer.mapquest.com Microsoft Virtual Earth www.microsoft.com/virtualearth Communities and
Neighborhoods Sperling’s Great Places www.bestplaces.net/docs/ Partner.aspx