ACRIS
The Automated City Register Information System (ACRIS) allows you to search property records and view document images back to 1966 for Manhattan, Queens, Brooklyn, the Bronx, and Staten Island. Maintained by the New York City Department of Finance.
Chicago Tribune Real Estate
Notable listings and sales of homes in the Chicago metro area
Christina Pulawski’s Tax Assessor Database
Listings of phone numbers, links, and multipliers for counties and other communities so you can find the market value of properties
Curbed
Real estate and urban design blog with area-specific editions for eight American cities and a flagship national site. Since 2013, Curbed has been part of the Vox Media family.
Eppraisal
Search by address for home value estimates; also gives the Zillow value for comparison.
Luxury Letter
Monthly newsletter tracking luxury real estate in New York City
Most Expensive Zip Codes
Property Shark has put together lists of the most expensive zip codes in the US, as well as the most expensive in Chicago, New England, and other regions. Also see Forbes‘ list of the most expensive zip codes in every US state.
New York State Equalization Information
The NY State Department of Finance’s list of equalization rates (the percentage of market value that the local assessed value represents) by county
StreetEasy
Search New York City and New Jersey properties for active listings, past sales, and past rentals by building and unit, as well as information by neighborhood. StreetEasy also has a site devoted to real estate in the Hamptons: Out East.
Zillow
The real estate site that has become a verb, a la Google. The site provides current market value estimates.
For links to non-domestic real estate information, look under “International“