The people at Forbes, with the help of some Internal Revenue Service data, have created an interactive map tracking where Americans moved during 2008.
The red lines indicate outward movement, while the black lines indicate inward movement, and they've separated everything into counties, so you can get a good look at the movement trends in to and out of Queens, Bronx, Kings, Richmond and New York counties. (Poor Staten Island, looks like they lose this round.) Another feature: you can click on certain spots on the map to find out exact numbers—for example, 14,581 people moved from Queens County to Kings County that year, with 21,054 moving from Kings to Queens.
For fun, and to perpetuate the coastal rivalry, we added the Los Angeles county map—looks like they lost a lot more residents than NYC that year.