Flow Map

http://en.wikipedia.org/wiki/Flow_map
I had to use Wikipedia simply as an example because all other examples had been used in student map catalogs. Cartographers have long used flow maps to show the movement of objects from one location to another, such as the number of people in a migration, the amount of goods being traded, or the number of packets in a network. The advantage of flow maps is that they reduce visual clutter by merging edges.I felt that this map was a great example of a clear in showing the distribution of wine from France in 1864.