Two years ago, as the economy began to falter, I realized that if I stopped buying my lunch and began bringing it in from home — I'm partial to PB&Js and Caesar salads, though both get all over as I eat — I could save about $55 a week and that, I quickly calculated, added up to a tidy sum over the course of a year. I wasn't the only one. Friends told me about bringing cans of soup to work to heat it up in the winter instead of buying it from a deli, or closely watching receipts to see where their money was being spent.