The True Size of...
The most common projection used on world maps is the Mercator Projection which maintains straight lines of latitude and longitude at the expense of distorting the size of landmasses as you move away from the equator. Greenland, for example appears much larger than it actually is. The True Size of is a web app that lets you compare countries with their true size by litterally dragging them to another place on the map to see the effects of Mercator Projection distortion.
The image shows Greenland as it would appear on the map if it was located at the equator.