Each holiday season, we relegate our unwanted gifts to the return bins of retailers across the country and never think of them again. But these items have a second life. “We help [stores] rapidly convert those excess items into cash sales,” said Bill Angrick, chief executive of Liquidity Services, a District company that works with many big-box stores. With Liquidity Services, retailers ship their unwanted merchandise to one of the company’s six distribution centers across the country as frequently as once a week. The company then inspects and sorts the goods before holding a private online auction for interested buyers, typically small businesses.