The daily articles at the National Center for Family Literacy's Wonderopolis are allegedly educational and supposedly aimed at kids. Don't let that fool you. They're just plain interesting, and make for addictive reading even for those of us who are, in theory, all grown up. For example, "How Does an Eraser Work?" doesn't just explain how erasers work — did you know they usually contain vegetable oil? — but also reveals how people removed pencil marks before Englishman Edward Naime invented the eraser in 1770. (They used rolled-up pieces of bread.)