Credit to FW:

Enroll today and use your Delta SkyMiles^® Credit Card from American Express in October and November and earn 25% more miles on all eligible purchases.

Enrollment required by 11/30/06. If you prefer to enroll by phone, please call 1-800-653-6051.

Note that if you’re already enrolled in a Double Miles program, you’ll continue to earn double miles. To view all the fine print or to enroll, see this link.