National Geographic Magazine
NG covers a huge range of interesting topics. I like the fact that the reader can choose how deep they want to dig into the magazine. Sometimes you just want a little brain candy, so you look at the pictures and maybe read the captions. Other times you want it all, so you read every word of an article about some obscure topic like "leaf-cutting ants of the congo". No matter how you decide to use it, you're guaranteed to find something new and interesting.