It's Arbor Day! One of the greenest things you can do to help the planet is to plant a tree. The National Arbor Day Foundation wants to make it easy for you to help the environment and beautify your yard. When you sign up for a six-month membership ($10), the nonprofit will send you 10 free trees to plant. You can also choose to send your free trees to a threatened rain forest or to one of the nation's national parks instead. To learn more, visit arborday.org.