In case you are still at home or just got up to go and get in line in front of a shop that sells the iPhone 3G, you might take a quick look at this page on Apple that lets you find the next retail location to purchase an iPhone 3G and tells you how to prepare for the purchase.

In the U.S. you need to bring a Credit card, Social security number, valid government-issued photo ID and current wireless account number and password or PIN (if you’re new to AT&T).
If you already own an iPhone, remember to sync it with iTunes one last time before you get your new iPhone 3G.

The Apple iPhone 3G info page lets you switch countries to get the specifics for your area.
Find the Apple iPhone 3G where to buy page here.

More iPhone 3G News.