CEO Hyman and co-founder Fleiss, both Harvard Business School grads, were all too familiar with the frustration of peering into a closetful of clothing but having nothing to wear. Their three-year old company lets women rent a designer dress at a fraction of the purchase price, making luxury fashion affordable, at least for a night. Wary designers needed convincing to come onboard at first, but what a difference three years makes: Today Rent the Runway has 3 million members who have rented outfits from over 160 designers. The site is especially popular on college campuses nationwide; a targeted program tasks 1,000 students to promote Rent the Runway at their schools, helping them develop entrepreneurial and marketing skills. De-stressing tactics: Hyman calls her parents on the way home from work every day; Fleiss goes for runs. –C.K.