Surprisingly simple ingredients you make, never buy

My favorite cooking/baking quote ever is actually from Carl Sagan: "To make an apple pie from scratch, you must first create the universe."

But what are basic ingredients you always "make" yourself, rather than buy from the store? I'm thinking simple along the lines of your own cinnamon sugar, or substitutions you always make, such as milk+vinegar/lemon juice in place of buttermilk.

Edit: if possible, please post how you make it and how you figured out to do so. I'm always fascinated by people who wake up one morning and decide to make their own yogurt and pickles.