From their newsletter:
Buy Seventh Generation Chlorine Free Diapers, and get a voucher by mail to get a free pack of our Baby Wipes. Rebate form available here. Valid only for products purchased between 12/9/2010 and 12/16/2010. Not valid for internet purchases. Be sure to check back for special internet offers coming soon.
If you already use this brand, and need some during that week, this may be a decent deal, but otherwise, I'd wait for sales.