For Earth Day, here's an app that helps you decide which products you buy, based on how green the company's manufacturing process is. GoodGuide is a free app in the iTunes AppStore. Simply scan the bar code of a product and it will show you a 0-10 rating based on the product's health, environmental, and social impacts. It also offers greener or healthier alternatives. Browse products by category, search for products by name or identify them with the built-in UPC scanner.