Take 2 tablespoons of blackstrap molasses before going to bed to relieve constipation. Molasses is too high in calories to use it as a daily preventative, but on an occasional basis, it can help to get you moving. It has a pretty strong taste, though, so you may want to add it to milk, fruit juice, or, for an extra-powerful laxative punch, prune juice.
Honey is also a very mild laxative. Try taking 1 tablespoon three times a day, either by itself or mixed into warm water. If it doesn't work on its own, you may have to pep it up by mixing it half and half with blackstrap molasses. Or, you can also mix 1 teaspoon apple cider vinegar and 1 teaspoon honey in a glass of water. Keep in mind, however, that honey (like molasses) is high in calories, so use it as an occasional laxative, not a daily preventative.