The study of human population growths and shifts is both a fascinating topic as well as a necessary prerequisite in understanding historical dynamics.
The following is a list of some useful sites:
Shows the increase in world population via a series of Maps : 1AD to 2050AD
Has some wonderful graphics - although the analysis seems stalled in the Ehrlich Population Explosion Paradigm where global population is increasing at an increasing rate (J-Curve). Better models argue that the rate of increasing is decreasing.
Nevertheless the website does deal with such issues as human carrying capacity, the AIDS phenomenon and the Demographic Transition
Demographic Transition (refers to type of society)
Stage 1: High Birth rate but fluctuating Death rate eg. 19th century Africa
Stage 2: Declining Death Rates but High birth Rates eg. Mexico
Stage 3: Declining Birth and Death Rates: eg, US
Stage 4: Low Death and Low but fluctuating Birth Rates eg. Sweden
Historical influence of climate change on World Population