Bank of America Corp. yesterday launched a new online-shopping Web site that enables customers to earn up to 20% cash back on purchases they make on the site. The "Add It Up" Web site features more than 270 retailers, including Walmart.com, Overstock.com, BestBuy.com and Barnes & Noble.com. Holders of BofA credit or debit cards enrolled in online banking can register for free. "Bank of America is giving customers a new way to stretch their money by getting cash back on purchases from hundreds of retailers they do business with regularly and letting them do it online at their convenience," David Owen, BofA checking and debit executive, said in a statement. BofA is not limiting how much customers can earn with the program. They can choose to redeem their cash-back rewards in either a checking or a credit card account. The Web-shopping portal concept is not new, but this is good time to launch a program like this, says Megan Bramlette, managing associate with Westbury, N.Y.-based Auriemma Consulting Group. "The whole idea that the bank can help save money in this economy will resonate with consumers," she says. "It says 'We're helping you,' and it's almost like a partnership."