When it comes to real-estate listings, multiple listings service Metropolitan Regional Information Systems (MRIS) is king. But only agents can access its data directly.

Owned by MRIS, Homesdatabase.com is the next-best option. It covers 22,000 square miles in five states, including DC, Maryland, and Virginia. One caveat: It doesn’t list street addresses, so you have to go to a broker for detailed information.

Brokerage site ZipRealty includes neighborhood data such as average household income and crime statistics. Real-estate search engine Trulia lets you sign up to get an e-mail alert if a specific address in its database goes on the market.

All three sites also let you search by house characteristics—such as number of bedrooms and baths, style, size, and price—and register your preferences so you’ll hear when any home that meets them becomes available.

Redfin lets buyers research neighborhoods, find houses for sale, and negotiate offers, all online.

Looking to rent? Check out Hotpads, which superimposes rental listings on interactive maps and includes photos as well as information on amenities and lease terms.

If you’re more interested in real-estate snooping than listings, check out Zillow or Eppraisal, which offer free home valuations and recent sales data.

This article appears in the December 2007 issue of The Washingtonian.