If you happen to have a jar of molasses, you can make actual brown sugar by adding 1 - 2 T. (light brown sugar v. dark brown sugar) molasses per cup of granulated sugar. Will keep your CC cookies to a chewy texture, as opposed to all white sugar which will make them crispier. Also, retains the caramel flavor many people favor in CC cookies. But each to his own, of course.
Speaking of crispiness, adding rice krispies is a cheaper sub for nuts in lots of baking. Also, adds a nice porousness to certain kinds of cookies.
Many are already familiar with this one, but just in case: when a baking recipe calls for buttermilk, sub 1 T. vinegar added to 1 cup milk for each cup of buttermilk called for.