SALE OF THE CENTURY: Those who haven’t blown their fall budgets yet can still do some damage this week at steep discounts. For its most recent project, Gilt Groupe, the e-commerce site that sells designer clothes at up to 70 percent off the original retail price, partnered with the Council of Fashion Designers of America. This Thursday, the invitation-only site will kick off a 60-hour sale of clothes from six CFDA members and their labels, including Derek Lam, Notte by Marchesa, Behnaz Sarafpour, Thakoon, Rachel Roy and Boy by Band of Outsiders. The pieces will mostly come from the designers’ fall 2007 and spring 2008 collections. And it’s all for a good cause: a portion of the sales benefits the CFDA Foundation.