CensusConnect has released a new Google Chrome Plug In to Enhance MLS Listing Sites.
It pumps "block level" census neighborhood information (% rentals on block, average age, income, % college grads, number of sex offenders within 1 mile radius, etc. ) directly into the listing rows of these sites automatically, so buyers can quickly and easily compare property characteristics of the properties at a glance without a lot of clicking, researching, etc.

This tool automatically adds socioeconomic characteristics (e.g. Ownership, Income, Employment, etc) within a city block of the property alongside your favorite listing websites (zillow, trulia, homesdatabase, local reators listings, etc.). In many cities, neighborhoods can vary wildly within a few blocks, and so "block level" data is critical to providing accurate neighborhood information. NO OTHER real estate product displays block level census data for properties

See the censusconnect website for more details: http://www.census-connect.com