National retailers are hosting events in honor of Earth Day, April 22. Target, the discount chain, plans to give free reusable bags to its first 1 million shoppers Sunday. Last year, the retailer warned, most stores ran out within a few hours. Office Depot and Old Navy are encouraging consumers to recycle their old stuff. From Sunday through April 23, consumers can take their used pens, markers or mechanical pencils to Office Depot to receive a coupon toward a new product by Sanford, which makes Sharpie, Expo and PaperMate brands. TerraCycle, a recycling company, plans to turn the used writing tools into trash cans and desk organizers. From April 22 to May 21, shoppers can drop their old flip-flop sandals in collection bins at Old Navy stores for the Flip Flop Replay. The rubbery flip flops will become playground equipment that TerraCycle plans to donate to communities nationwide.