According to the US Census Bureau, as of 18:27 UTC Nov 3, 2011, there are 6,972,600,139 people on Planet Earth. Watch the World Population Clock here.
Oh wait, at 18:29 UTC, there are 6,972,600,403 people on Planet Earth.
This is an important event. The concepts of Peak Water and Peak Oil are strongly linked to global population increase. This is a truly monumental event.
As usual Wiki has some of the important answers. Refer to this page.
Oh oh, at 18:32 UTC, there are 6,972,600,828 people on Planet Earth.
Enjoy the 7 billionth birthday-day.