Population Reference Bureau
Phone: 800.877.9881
Fax: 202.328.3937
E-mail: popref@prb.org
http://www.prb.org
Click on "Publications" on the top menu bar. Click on "Population Handbook."

U.S. Census Bureau
http://www.census.gov
For education-related information, click on "For Teachers and Students" under "Special Topics."