Huge sales on food items at the supermarket are so tempting. It's an opportunity to save lots of money and ensure plenty of cheap meals (and "pantry shopping" when you're out of money or time) for days to come. But food isn't cheap if it spoils and you have to dump it, and some foods have a shorter shelf life than you might think. Here's an overview of foods to stock up on, and those you should buy as needed.