There is a great magazine called, Zoobooks that introduces kids to the wonders of nature and teaches them about the world around them. Right now on Groupon there is a great deal on them: $10 for a year subscription (instead of $30)!
There is also one called Zootles and Zoobies for younger kids. These are great and the price is fantastic! You can also purchase a 2 year discounted rate too!
Use this link and then click on "Goods." Scroll down and you will see the Zoobooks there.