Attending a lot of parties and Summer soirees is never a problem in our books — unless you have nothing to wear. That said, we scoured the virtual sale racks and found pieces you can instantly add to your black-tie attire arsenal. From pretty lace sheaths from Christopher Kane to knock-'em-dead footwear from Yves Saint Laurent, you don't want to miss these deals. Did we mention some of our picks are marked up to 70 percent off? Now that's a deal.