Apps for spatial thinking

While in California for the Applied Geography Conference, a friend introduced me to two apps for iPhone (and iPad) to promote geographic (and geometric) spatial thinking -- "Stack the States" and "Stack the Countries."  There are "lite" versions of both, but full funtionality is only $0.99 (for the states).  Not only is the user asked to indentify the state/country by shape, but they are asked question about neighboring states, features, capitals that go beyond rote memorization of the "Fifty Nifty United States" song. 

I also have several other "geographic" apps on my iPhone (3G -- I can't wait to upgrade to the 4Gs). 

• ESRI Business Analyst (BAO)
• ESRI ArcGIS
• Google Earth
• Park Ranger
• Around Me
• NASA

What are some apps you have found that you can use in social studies education?