REALTOR.com®: Geared towards consumers. Lots of tools and resources. Free resource maintained by the National Association of REALTORS®.
REALTOR.org®: Geared towards real estate agents, but also has good information for consumers. Free resource maintained by the National Association of REALTORS®.
The Wiser Home Buyer: A simple, easy to read resource about the basic steps involved in purchasing a home.
Walk Score®: This site calculates a "walk score" for any address you input, based on proximity to transportation, services, shopping, and more. Free.
Neighborhood Scout®: Website that consolidates all data on crime, property value, and schools, sorted by neighborhood. City descriptions and demographics. Some free information, but requires subscription to see detail. $19.99 / month to $39.99 / month depending on term.
Spot Crime: Allows you to see exactly what types of crime occured when and where on a google map. Free.
Home-Ownership Related Services
Angie's List®: A customer review site of all housing-related service providers, as well as health providers and other services. Monthly fees range from $5 to $10.
Local Property Databases
Registry of Deeds: Deeds and floorplans for any property in Massachusetts.