We know that babies are the best accessory in Hollywood. No starlet has truly made it until she has become a mom (Welcome to the club, January Jones). That means there are some mad stylish mamas out there in tinsel-town. We were reading one of the most talked about tomes of this spring, Piper Weiss' 'My Mom The Style Icon' and we got to wondering who in Hollywood has the best mom style. We asked Weiss at her bash with Coach celebrating the release of her book to identify the Hollywood moms with the best fashion sense. The big winner: Michelle Williams, mom to the adorable Matilda.