Apple has started sending shipping notifications to customers that pre-ordered the iPhone 4S last Friday. Some orders still say "preparing for shipment," but most customers have noticed that the iPhone 4S has been shipped with a delivery date of October 14th.
Pre-orders are coordinated with UPS in the US to ensure that shipments don't arrive before the confirmed delivery date, so don't get your hopes up for an early iPhone 4S delivery to your doorstep...