I read about this deal over on the Anandtech Hot Deals subforum. If you have an eligible card from American Express, you can get a free, lifetime membership to ShopRunner.
I hadn't even heard of ShopRunner, but part of their service is free, 2 day shipping from the businesses that work with them. For us hardware geeks, these include MacMall, Tiger Direct and Newegg.
You have to keep your Amex card as the default payment to remain in the ShopRunner service, but you are not obligated to pay for anything with it. You can always opt to use a different form of payment.
Seems like a fairly good deal, and it looks like it is meant to be a competitor to Amazon's Prime membership.
Here is the link for the ShopRunner sign up: https://www.shoprunner.com/americanexpress