International Statistics - from the Census Bureau. Provides dates for national census and links to other national statistical agencies
Population Reference Bureau
Information on U.S. and international population trends. Their publications include the World Population Data Sheet, which includes key indicators from geographic areas of populations of 150,000 or more.
Population Statistics: Historical Demography
Historical, demographic and statistical overview of the population of all the countries in the world, their administrative divisions and their important cities.
Official government web site for Canadian statistical information.
World Development Indicators
Contains socio-economic time series data on countries.