Here’s a very interesting Page I found on the current and historical developements of the human world population it provides very accurate statistics on the developement from the start of our civilisation up to the present.
It also comes with a detailed live-count. don’t look at that for too long though, it might be depressing… .
However in order to estimate the population – developement before 10000 BC I found these Wikipedia-Articles very helpful:
Also very helpful is Hyde, the History Databas of the Global Environment: