UW Center for Studies in Demography and Ecology:
http://www.csde.washington.edu/

US Census:
www.census.gov

Statistics from US Federal Agencies:
http://www.fedstats.gov

Guttmacher Institute:
http://www.agi-usa.org

National Center for Health Statistics:
http://www.cdc.gov/nchs

Internet Guide to Demography and Population Studies:
http://demography.anu.edu.au/VirtualLibrary/

Center for International Earth Science Information Network (Columbia Univ):
http://http://www.ciesin.org/

Population Reference Bureau:
http://www.prb.org

My lab website:
http://depts.washington.edu/endolab/