Visualization of shipping routes from 1750 to 1855 APR 17 2012
This video is a visualization of the how ships moved goods and people around the world from the mid-18th century to the mid-19th century.
Here's more on how it was done.
This shows mostly Spanish, Dutch, and English routes -- they are surprisingly constant over the period (although some empires drop in and out of the record), but the individual voyages are fun. And there are some macro patterns -- the move of British trade towards India, the effect of the American Revolution and the Napoleonic Wars, and so on.
There are times in the video when a single nation dominates all of the shipping traffic...the British in the early 1800s and the Dutch from the mid 1830s on.