Apple allows in-home online iPhone sign-up
Apple has now begun offering a way for those that wish to sign up for the Apple iPhone 3G with AT&T service can do so online prior to visiting an Apple store.
Apple’s online sign-up requires the user to enter billing information, review eligibility and pricing, and then select your AT&T rate plan.
Once this has been done you then visit an Apple store to complete the purchase of your Apple iPhone 3G.
The “in home” option has generated some speculation, but as it turns out you still need in store activation upon your iPhone purchase.
Source — macrumors