With Amazon in mind, Wal-Mart to offer free shipping for 30 days

(Reuters) - Wal-Mart Stores Inc on Wednesday launched a free 30-day trial of ShippingPass, its two-day shipping program for shoppers in the United States, as the world's largest retailer looks to take on Amazon.com Inc's Prime subscription service. Wal-Mart said that existing ShippingPass subscribers will get one month free. Wal-Mart's two-day service costs $49 a year.