For American Express cardholders, ShopRunner still offers a ShopRunner 1-Year Membership for free when you enroll with your American Express card. That's tied with our mention from last month as the best offer we've seen for this shipping service since December, when we saw a free 1-year membership that was open to anyone. It includes unlimited free 2-day shipping, free shipping on returns, and more. Some of the vendors that use this service include Toys "R" Us, newegg, Lord & Taylor, Calvin Klein, eBags, and drugstore.com. Be sure to cancel before your subscription is up, or you'll be billed for another year at full price, currently $79. Deal ends May 15, 2014.

Of note, American Express cardholders that are current ShopRunner members can get ShopRunner 1-Year Extension for free when you link your American Express card to your account.