Cost of living: United States cities and metropolitan areas
ACCRA Cost of Living Index
Measures relative price levels for consumer goods and services in participating areas. The average for all participating places in each quarter equals 100, and each participant's index is read as a percentage of the average for all participating places. The above link is for current Harvard only. There is also a fee based service.
Consumer Price Index
Includes city data, but the index is to a year rather than a city average, so it is an indicator of inflation but not cost of living.