Free real estate sites
Commercial Investments 
If you are looking to buy or sell some commercial real estate this is the place to start. Find properties, professional real estate agents, or get loan quotes all in one convenient place. Free membership is required and gives you access to unlimited property searches and listings as well as their enhanced services. You can find properties both for sale and for lease from a multitude of sources and in hundreds of locations.
Commercial Real Estate
CityFeet is the premier commercial real estate network. You can find commercial properties for sale or lease as well as brokers and executive suites. When you place a listing with them you get exposure on over 125 website including sites like the New York Times and the Washington Post! Auctions, appraisals, and other services are also available to make your listing or property search as easy and convenient as possible.