The new $1.18/domain GoDaddy coupon ($1 + the $0.18 ICANN fee) will expire on the 31st of December 2011 at 11:59 PM EST or after it has been redeemed 10,000 times. It cannot be used for transfers or renewals, only new registrations. One domain per customer and it is not possible to use PayPal or AliPay.
It’s not limited to dot coms though, it works for other TLDs as well: . net, .org, .biz, .us, .ca, .in, .co.uk and .mobi. have fun