The battle for the Christmas shopping pie has hardened between retail behemoths and online shopping firms, with most retailers coming up with shopper-friendly offers to lure holiday customers.

This year, online sales are expected to peak about 10 days before Christmas as consumers realize they are running out of time to get presents under the tree.

Amazon.com offers free shipping on $25 minimum orders and its Amazon Prime, a membership program that offers free two-day shipping for an annual membership fee of $79, is available year-round.

On the other hand retail stores like Wal-mart have been in a battle to win over online shoppers from online retailers. Last week Wal-mart offered free shipping on 60,000 items including TVs with no minimum purchase through December 20.

On Wednesday, Best Buy Co. became the latest retailer to offer free shipping. The electronics giant said it's offering free shipping on hundreds of thousands of products through Dec. 21.

Larger items such as TVs and appliances and smaller ones such as netbooks, laptops and iPads are excluded by Best Buy and others.

J.C. Penney offers free shipping on orders of at least $69 while Target's free shipping minimum is $50.

For retailers, it's a competitive advantage. For consumers, it's great, said Luke Knowles, founder of freeshipping.org and freeship pingday.com, according to Dallas Morning News.

“Attaching free shipping to a membership program is being mimicked by others including Kmart, Sears, Overstock.com, Borders and Barnes & Noble,” Knowles said, adding that he has signed up more than 760 retailers to waive shipping costs on this year's Free Shipping Day, Dec. 17.

According to him it’s tougher for the smaller players to match with big players with a full season of free shipping. “It is easier for bigger companies comparatively as they can offer free shipping because they have more distribution points throughout the country,” said Knowles.

The biggest online spending day falls between Dec. 10 and 15 and occurs early in the week, said Andrew Lipsman, industry analyst at comScore Inc. That'll probably be Dec. 13 or 14 this year, he said.

Last year, the biggest online shopping day was Dec. 15, when consumers spent $913 million. The second-busiest day was Cyber Monday, the name given to the Monday after the long Thanksgiving weekend, when sales totaled $887 million, according to comScore.