Today AT&T stores will open early with most stores opening the doors at 7:00AM to begin the launch of the iPhone 4 for those customers that weren't able to pre-order the phone. The retail stores will have a limited supply of phones available and lines are already being reported around the country. AT&T has also updated their website and made the iPhone 4 available to order. I've been told by an AT&T sales rep that orders could be received within 3-5 business days.
Photo Source: MacRumors.com (KTasm) from Longanville, GA