This interactive population density maps makes it easy to see where the high density pockets of humanity exist around the world. Hit the slider at the top of the page and it lets you slide from 5 people per square kilometer to 500 people per square kilometer. Watch the world map change as you move the slider towards higher density.
This map is based on a population of 25 person per kilometer.
Courtesy of Density Map by designer Derek Watkins, this map makes it dead simple to understand distribution of population around the wold. Read his blog entry on the map to learn more about how he constructed it.