According to Apple's iPhone stock checker, every Jun 30 2007
According to Apple's iPhone stock checker, every single Apple Store in the country currently has iPhones available.
Update: That page only updates once a day at 9pm for the next day's stock. So when it says there are iPhones in stock at 3pm, that's not necessarily the case. (thx, jeremy) At around 11:30 am ET today, Jake Dobkin reported "plenty of stock, no wait to purchase".