Problem:
Often times, recipes call for using a little bit of stock (vegetable, chicken, beef) to prepare a sauce or add flavor. I almost never use all of the stock that comes in a can or box. Every time I cook certain recipes, I need to buy new stock and only use half of it! (Yes, the thriftiest thing would probably be to make my own stock, but, this isn't Martha Stewart's blog, it's mine and I just ain't got time like that).
Solution:
Pour the extra stock into ice cube trays, freeze and bag for later. I date the bags of cubes so that after 6 months or so, I'll replace. A cube equals roughly an ounce. Ergo, 4 cubes = 1/2 cup, etc.
Bonus thriftiness:
Keep an eye out for stock after big holidays, like Thanksgiving and Christmas. Stores load up on extra stock (used for roasting turkeys, creating gravies, etc) pre-holidays and then usually sell them for at least 1/2 price immediately after.