A smart, swapping site for kids clothes, toys, books Say goodbye to thrift stores, garage sales, and flea markets. Thred UP, a new online swapping platform, allows parents to swap kids clothing, toys, and books using the Internet and U.S. mail service. SmartPlanet talks to the company's founder, James Reinhart, about the service and why he decided to create a business targeting the way kids items are bought and sold.