Google has announced the addition of public data comparison charts through Google searches. Currently, only data for unemployment rates and population is available, but Google does promise additional data in the future. Data is from the U.S. Bureau of Labor Statistics and the U.S. Census Bureau's Population Division.
To use this feature, go to Google and type either "population" or "unemployment rate" (remove the quotes), followed by a state or county. Click on the first search result, and a graph will appear showing that data. You will also have the opportunity to add additional states and counties to the graph. For example, here is a graph showing the populations for Wayne, Oakland, and Macomb counties: