Beans and legumes are among some of the most nutritious of vegetables. Easy to prepare, they also hold up very well to reheating. And, believe it or not, beans do very well in sweet as well as savory applications. Adzuki bean paste is a very popular filling in Asian snacks, and have been used to prepare ice cream and milk shakes. Chickpeas can be candied or ground up and fried to form patties.
But perhaps the most onerous item about using legumes (well, aside from their notorious reputation for promoting flatulence in some people) is the length of time to get them ready. My favorite thing to keep around are lentils. They are quick to cook, be ready in 30 minutes without needing the presoak. All you need is water and salt, but I try to bump up the flavor quotient with the addition of other spices, and can toss in other vegetables or meat.
Cooking tip: you can retard the softening of lentils with the addition of an acid. Therefore, if your lentils have reached the level of doneness but you would like to keep heating them (say, to extract additional flavor from dried herbs or some added sausage), then put in some lemon juice. The firmness of the lentils should stay the same through multiple reheatings.