http://www.apple.com/iphone/storecredit/
Requests for the $100 credit must be submitted by November 30, 2007.
You must activate your iPhone with AT&T prior to submitting your claim. Once you activate, return to this page after 24 hours to request your credit
As promised, Apple posts the information on the $100 credit for iPhone purchased before August 22nd, 2007.
$100 Apple Store Credit for Early iPhone Owners
If you bought your iPhone before August 22, you may be eligible for an instant $100 electronic credit toward the purchase of products at the Apple Retail Store or the Apple Online Store. See the terms and conditions below for more details.
To receive your credit, follow these three easy steps.
Step 1: Identify your iPhone
To confirm eligibility, simply enter your phone number and iPhone serial number in the fields provided.
Step 2: Enter your access code
You will receive an SMS text message on your iPhone containing the access code to redeem your $100 credit. Enter your phone number and your access code in the fields provided to generate an electronic store credit.
Step 3: Get your $100 Apple Store credit
You will receive a $100 electronic store credit to purchase products at the Apple Retail Store or the Apple Online Store.
Related: