Six Sigma, a wildly popular cost-cutting tool for manufacturers in the 1990s, has resurfaced this decade in a new arena—retail. Some of the country's largest retailers and grocers have implemented Six Sigma programs over the last few years and shed millions in superfluous costs. BusinessWeek asked Six Sigma consultant SSA&Co. to share some of the most innovative and cost-effective uses of Six Sigma that they've encountered in the retail realm.