Scroll down to "Percent Change, 1990-2000 and Population Density, 1990" http://www.census.gov/population/www/cen2000/atlas/pdf/censr01-103.pdf
Found the digital, interactive version of the NYTimes Election 2004 map: http://www.nytimes.com/packages/khtml/2004/11/03/politics/20041103_px_ELECT_G...
Try the Bivariate example down the page (GeoVista is a great group up at Penn State): http://www.geovista.psu.edu/grants/nci-esda/software.html#
Singles in the U.S.: http://1.bp.blogspot.com/_JRzWnNjXRV0/Rydib_lM3tI/AAAAAAAAACE/TWRLM9d_H4c/s16...
Pie chart graduated symbol map of obesity: http://hci.stanford.edu/jheer/files/zoo/ex/maps/symbol.html