Buttermilk is excellent in baked goods, and also as a and salad dressing base. It lends a rich, hearty flavor with fewer calories than milk or cream. The tangy flavor of buttermilk goes well with sweet fruits such as peaches, cherries, and pears, particularly as creme fraiche.
The acidic properties of buttermilk make it an effective and flavorful marinade, particularly with poultry. It is used as an acidic ingredient in baked goods to combat dingy grayish discoloring often caused by the chemical reaction of blueberries, walnuts, and other foods that give off a blue cast. It also promotes browning of baked goods and improves texture.
Many prefer dipping meat, poultry and fish in buttermilk rather than milk before coating for frying and baking.
Unless you feel adventurous and are not concerned about failure, use recipes specifically designed with buttermilk as an ingredient rather than substituting buttermilk for milk.
In savory recipes, this is not such a concern as usually no leavening is involved, but be aware that a slight tangy flavor will be imparted to the food, much like that of sour cream or yogurt.