Interstate Bakeries is one of the more fascinating success stories in an industry not known for surprising turnarounds. The core of the company's growth is a collection of once-moribund brands Interstate bought from Ralston Purina in 1995. Ralston had all but written off its ailing Continental Bakeries unit, which produced such well-known supermarket staples as Wonder Bread and Hostess snack foods. But through savvy marketing and modern production methods, Interstate has been able to revive the brands and wring out cost savings of $120 million from its Continental purchase in just two years -- a year ahead of schedule.