According to MacNN, Apple has almost completely sold out of its iPhone 3G stock. According to their report there are only 3 locations left that even have stock. Only New York, California, and New Hampshire even have any iPhone left to speak of…and not one of them has an 8GB iPhone available.
AT&T is reporting that it could now take as many as 3 weeks to actually receive your iPhone if you pay for it today and get on the waiting list.
Overall, it looks as though Apple seriously under estimated the demand for the new iPhone. There is no official word yet on when Apple will have a replenished supply of iPhones for consumers, but you can rest assured that someone, somewhere, is losing sleep over solving that problem.