In the fall of 2011, a New Zealand oil spill sparked a chain reaction of frenzied knitting activity. A local yarn store posted an urgent call for penguin sweaters to warm the affected birds and prevent them from nibbling the oil off their feathers. In less than a week, knitters from around the world had crafted and delivered far more sweaters than there were penguins. While there’s nothing new about activist knitting, today’s fiber warriors respond to urgent causes more creatively and enthusiastically than ever. By applying their flying fingers to unlikely patterns and constructing sometimes unusual objects, they address challenges that are social and environmental.