According to Apple’s iPhone availability checker, the iPhone 3G is sold out at every Apple store in the US (except 8G at the Kahala store in Honolulu, HI and 16G white at Rockingham Park, NH & Fifth Ave NYC).
Last week in Vancouver I saw lines of people waiting to buy iPhones at every Rogers & Fido store, including a kiosk in Pacific Centre. The iPhone 3G appears to be selling even faster than the original model.