I ordered through Sprint. If you search their site for "check order status" you can find a link for doing precisely that. Then plug your order number in there and then bam! I have a nice little paragraph that says;
"Status: Thanks for pre-ordering. A shiny new iPhone is waiting for you in our warehouse. Excluding extreme circumstances, you will have your device Friday, Oct. 14 or Saturday, Oct. 15. During the pre-order period, we will send you a shipping email and tracking number. Your tracking number may not be updated until Oct. 14. Questions? Visit sprint.com/preorder."