Trulia did not waste any time with its recent acquisition of the mapping startup Motivity. Go to http://trulia.movity.com/ to check out "Rent" vs. "Sale" costs, mapped by major U.S. cities, pulling from sources, "Trulia.com, Census.gov, RealtyTrac.com, BLS.gov and Moody's Economy.com." I am guessing that Trulia will be using the new data mapping capabilities on a variety of interactive reports in the future.
"Trulia's Q1 2011 Rent vs. Buy Index provides guidance to help you make a smart decision on whether it is better to rent or buy in each of America's 50 largest cities by population."
Other metrics availble are: