"Who Moves? Who Stays Put? Where's Home?" [pewsocialtrends.org] is a set of geographical data visualizations that display patterns of domestic migration, that is movement of people among the nation's regions and states. They show gains and losses only from people who move from one state to another. The maps use estimates from the American Community Survey for 2005-2007, and from the American census from the 1980, 1990 and 2000 census.
These maps seem unique in their neat design and minimal but effective use of animation and stylized graphics. Arrows "flow" from one side to another. The thicknesses of the arrows reflect the size of the flows. Nicely ordered data simply adapts while hovering the mouse. 2 simple columns of ranked "magnet" and "sticky" states invites for exploration.