PayPal is already willing to stand up to MasterCard and Visa as a viable payment alternative in brick-and-mortar stores; now it plans to take on the giant of Internet retailing, (NASDAQ:AMZN), and come after it where it can have a big impact: shipping.

The eBay (NASDAQ:EBAY) subsidiary just announced it's running a limited-time offer to give free two-day shipping for online purchases at nine different retailers. With no minimum purchase amount and no fees, PayPal is willing to go head-to-head with Amazon's Prime, which lets you get "free" shipping for a $79 annual fee.

Sort of. As mentioned, there are only nine retailers participating in the promotion at the moment, including Aeropostale, Dick's Sporting Goods, and Levi's, which is just a fraction of the partners Amazon has in its stable, or the thousands of retailers ShopRunner offers -- but there's nothing to suggest it's a service that can't grow over time if successful. 

Moreover, as retailers themselves explore more ways to enhance the shopping experience with free ship-to-store alternatives such as those developed by Wal-Mart and more recently Target, it's clear that getting a product from the computer screen to the customer's hand is becoming key to closing the sale.

This seems to be part of an under-the-radar move by eBay to become an integral part of the online shopping experience, moving beyond its role in online auctions. In addition to this pilot program and PayPal's appearance at store registers, it's also expanding its BillMeLater lending service through private-label credit cards issued by partner Alliance Data Systems; developing its eBay Now same-day delivery service to compete against Google's Shopping Express and, to a certain extent Amazon, which is building out its own distribution center network to be closer to its customers; and gaining greater expertise in mobile payments with its recent acquisition of Braintree. 

At 27 times earnings, eBay might seem pricey compared to its rivals; however, take into account analyst estimates of its growth prospects, and suddenly a multiple of 17 times future earnings makes it look more attractive than Amazon or even

Shares have swung broadly between $50 at the bottom and $57 at the top for most of the year, topping and bottoming several times as investors take measure of what the online auctioneer is attempting to achieve. As it rolls out these new initiatives and makes its services more vital and sticky with consumers, the cumulative effect is calculated to add up over time.

With no let-up in sight for the growth of e-commerce, especially as we approach the prime holiday shopping season -- Black Friday shopping topped $1 billion for the first time ever last year -- and the broad appeal of mobile payment options, becoming the place to turn to for fast, reliable, and cheap delivery will make eBay's financial services sector an even more valuable asset to consumers -- and perhaps its stock more valuable to investors.

Fool contributor Rich Duprey owns shares of Aeropostale. The Motley Fool recommends, eBay, Google, MasterCard, and Visa. The Motley Fool owns shares of, eBay, Google, MasterCard, and Visa. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.