The new iPhone 3G S officially launches on June 19th. According to AppleInsider Apple already informed the first people who pre-ordered the iPhone 3G S on the Apple Store that their iPhone 3G S started to ship.
The iPhone 3G S ship directly from the manufacturing plants in China. So most likely they will not arrive before the June 19th release date.
Apple does promise though to deliver the new iPhone 3G S on June 19th, when it will also be available in stores. If it works out than ordering the iPhone 3G S online was the smartest move and is way better than sleeping in front of stores or running around to find a store with iPhone 3G S stock.

Over the weekend we reported that rumor has it that AT&T already sold out their online inventory of the iPhone 3G S.
More iPhone 3G S News.