While surfing around the web, I found a statistic that said there were roughly 298 million people in the United States right now.
That surprised me. I thought we were hovering around 250 million. So I went to the source: the U.S. Census Bureau. On that site they have a population clock, and sure enough, we're at 297+ million people here in the US of A*. Wow.
According to that site, the population has a net increase of one person every 10 seconds (accounting for births, deaths, and net immigration). Given that rate, and the current number, it looks like we'll hit the 300,000,000 mark in about 253 days, in early September (the 9th, according to my calculations). Since they use a formula to calculate the population instead of actually counting people, this is approximate, but probably close.
I'm not one for arbitrary milestones, but I have to admit that's pretty interesting. I'll have to check back on that clock in a few months and see how close we're getting.