I use a lot of buttermilk in our daily baking as it gives my baked goods a nice bright flavor and a pleasant light texture. Just yesterday I made a batch of my corn muffins using regular milk as I had no buttermilk, and today I made a batch with buttermilk and they were noticeably better. My scone recipe also calls for buttermilk (recipes for corn muffins and scones are on my Cheat Sheet), and buttermilk is notoriously good for pancakes, waffles and biscuits. Cultured milk may also be more beneficial health wise than regular milk.
On a recent trip to the grocery store I realized that at $2 a quart, buttermilk costs twice the price of regular milk. But it is very easy to make at home, so I have been making my own. Basically, you use a small amount of purchased buttermilk as your starter culture, mix it into your regular milk, and let it sit until it's done. It's much simpler than making yogurt as it sets up nicely at room temperature so you don't need any special heating source or equipment.
Start by washing your chosen container in hot water to be sure it is clean. I use a glass pitcher, adding about a third of a cup of cultured buttermilk (I don't bother to measure) and filling the rest up with fresh milk. I've been using whole milk and it turns out very good. I give it a stir to mix it up and then cover the pitcher with plastic wrap. Then I just let it sit on my countertop. It takes about 12 - 36 hours to set up. When it looks nice and thick it's done and I move it to the refrigerator.
Then I just save a bit at the end to use to start a new batch. I do wash the pitcher out between batches. (Obviously if you end up with milk that looks or smells off you might have ended up with some sort of stray bacteria or contamination, but I've never had that happen.)