Frugal non-refrigerated foods?

I recently came to the conclusion that I spend way too much money on food, coffee, and other drinks. The obvious solution would be to eat at home more, but unfortunately it's difficult for me to get home in the middle of the day to eat.

What are some good foods that won't go bad if I don't refrigerate them? I'm thinking fruits, nuts, bread, and maybe warm food in a canteen.