Beans, legumes, and grains all fit the bill here. They are extremely versatile and work well in many ethnic recipes, such as Italian and Mexican. They are easy to make, and can be very flavorful without lots of work.
Canned beans are wonderful in salads, chilies, soups, and fillings for burritos and quesadillas. Grains such as brown rice, quinoa, barley, and millet make great pilafs that go well with chicken and fish, and also work well in stir-fried dishes. One of my favorites is a stir-fried rice—a healthy fried rice, if you will—with shrimp, chicken, green onions, and chili pepper. I can eat it five nights a week. Many grains come in fast-cooking varieties, but try to stick to whole grains for the best taste and health benefits.