PropertyShark. This link opens in a new windowA "property research tool," originally covering the New York real estate market, but since expanded to cover 46 other American states, which features searchable data on property foreclosures, auctions, sales, rentals, value estimates, property owners, and sales history, as well as tools to generate reports and targeted mailings, and dynamic maps to visualize data and queries. Data is searchable by address, parcel ID, building class or type, use type, and various physical features of a building or lot.