When your beans and rice are done boiling, strain them and add in some cooked frozen corn. This meal goes great with fresh veggies, cheese, hot sauce, and sour cream depending on your budget. It is a good way to get protein in your diet when you can't afford fresh meats.
On a budget I will do black beans, corn, rice, a chopped tomato, and some tapatio. When properly portioned this can be less than a dollar a meal. When I have a little extra I will use cilantro, lime, salsa, sour cream, cheese, salsa, and may be some lettuce.
Rice and beans are a good way to make a meal more filling and more cost effective. :)