I've been broke so often that I consider myself something of an expert on this subject. Here are a few reviews, which I hope will be of use to the nouveau pauvre:

• Peanuts: Filling, full of protein and fat (if you're worried about gaining weight, you've got too much money to be looking at this node). Excellent combined with raisins.
• Ramen: An old geek favorite. Extremely filling because it's hot and salty. But contains no nutritional value. My roommate suggests adding eggs for protein. I prefer vitamin supplements instead.
• Beans and rice: Filling as hell, contains a complete protein, can be spiced with anything. Goes well with curry.
• Cheap frozen foods: come in many different styles and flavors, so they'll stave off death from both starvation and boredom. Consult your grocer's freezer.