Google Public Data provides visual representations of U.S. data at the national, state and county levels.
GapMinder displays data from 430 social indicators (demographics, heath, environment and much more) in graphs that "move" the data over time periods. Either browse data or use search box in upper right-hand corner.
(click on image to enlarge)
Example: "Changes in Life Expectancy 1801-2007 by Country and Income"