FindTheBest created a cost of living index based on 2013 family budget estimates for housing, taxes, healthcare, childcare, transportation, and "other necessities" (like food) from the Economic Policy Institute to compare, in over 600 counties and metro areas across the US, where your dollar goes the farthest.
The average overall index for US cities and metro areas is 100, so a city with an index of 120 is 20% more expensive than average, and a city with an index of 80 is 20% cheaper than average.