The United States has a "Clock" that reports what it thinks is the current US, and World Population at any given moment. The Clock is updated every five minutes based on the suggested rate of births, and deaths. Currently births exceed deaths, and the population climbs by the minute.
A screen shot shows where it is at the time of this blog posting.
So roughly 6.9 Billion people are on the This Shrinking Planet as of February 2, 2011. To make things interesting, why not check out the ever changing Population Clock yourself, click here.