Check out this cool graphic on The Economist magazine website.
It compares American states to other countries with similar populations and similarly sized economies (measured by GDP).
Vermont has the nation's smallest economy. It is the size of Yemen.
California's is the size of Italy. If it were a country it would be one the world's ten largest economies!
Everyone knows that the United States has a large economy (by far the word's largest), but it's weird to think of the fact that it is larger than the aggregate economy of 50 different countries.
Besides helping the reader conceptualize economy and populations sizes in new ways, the graph is very interactive.
You can click on the individual states for more details.
There is also a similar graph for Chinese, Indian and Brazilian states or provinces. I like the layout of the international graphics better because the graphs are on the side of, rather than below, the map.