Flow Map

http://www.mundi.net/maps/maps_014/
Flow maps are "a mix of maps and flowcharts, that show the movement of objects from one location to another," (Doantam Phan, Stanford University). They depict things like the number of people in a migration, the amount of goods being traded, or the number of packets in a network. They can basically be utilized to show the movement of almost anything imaginable, whether it be abstract or concrete. Things that can be shown on the maps are the direction what the variable is, where variable is moving, how much of the variable there is moving, and other general information.
The flow map featured above shows telecommunications traffic in Europe.