Take one of DataMasher’s 90-odd datasets (demographic, economic, energy, health, etc. data by US state), add/subtract/multiple/divide it by another dataset, and plot the results as a choropleth map (plus get the results in tabular form):
Mashups are posted publicly for comment and ratings. Results may be significant, or be totally devoid of meaning; YMMV. DataMasher makes no claims as to the statistical validity of any of the maps created. You can also select and plot individual datasets by themselves. There’s a short video on how the process currently works, and DataMasher promises more datasets and capabilities are coming.