Free shipping has already become one of the most attractive promotions retailers offer.
Walmart offers (through Dec. 20) free shipping for nearly 60,000 items.
Gap recently dropped its required minimum purchase for free shipping in half -- to $50.
L.L. Bean started offering free shipping with no minimums this summer (that will end Dec. 20).
Zappos.com, the Amazon subsidiary famous for its comprehensive shoe lineups, offers free shipping to customers and returned shoes from customers.