One of the least obvious frugal tools in my kitchen is the humble plastic ice cube tray. I keep several of these around to use whenever I have a surplus of several different kinds of food. By freezing stocks, sauces, fresh herbs and even some soups, I save up what I can't use immediately in a stable form and a convenient size. This lets me buy some items in quantities much, much larger than my two-person household would otherwise be able to use.
For instance, there's a particular tomato sauce that I like to use on our homemade pizzas. I first came across it in an expensive antipasto bar at our local upscale grocery store. I soon identified the brand of sauce that they were selling and sourced it from an Italian deli/grocery store. The cans were large, but the price was great. So I opened the can and used just what we needed for our dinner. Then I filled three ice cube trays full of tomato sauce for three days running. I ended up with frozen cubes of tomato sauce, which lets us thaw just a tiny bit of sauce at a time, just enough to lightly sauce our pizza pies. I store these in a ziploc bag in the freezer.
I've done the same with coconut milk. Cans of coconut milk inevitably seem to contain more than my recipes call for. Rather than trying to come up with an additional use for the remaining milk, I just freeze what's left over. Same goes for chicken and beef broth or any leftover cooking liquid. The size of the frozen cubes makes it easy to garnish with small quantities. I've also used frozen cubes of broth to rapidly cool down soups that need to be refrigerated. I try to prepare the soup with a little less liquid than called for when I want to do this. So when the cubes melt, I don't have soup that's too thin. When storing broths this way, or anything that looks less distinctive than tomato sauce, I label the bag so I can easily distinguish between beef broth and chicken broth. It saves rummaging around in the freezer and letting out too much cold air.
One of the less intuitive uses for the ice cube tray as a stocking up tool is preserving fresh herbs. When basil is in season, I grow a lot of it, clean it, chiffonade the leaves and pack them tightly into the compartments of a tray. Then I cover them with olive oil and freeze. The cubes of oil and herbs make a great accompaniment to meats, some soups, pasta dishes and of course, pizzas. Naturally, frozen "fresh" herbs aren't quite as good as the real thing. But it's better than letting anything go to waste, paying through the nose when it's out of season, or worst of all, going completely without the taste of basil in the winter. I try to match the oils with the herbs. Olive oil goes with parsley, basil and sage. Canola oil goes with Thai basil, mint and cilantro.
Hope you found this tip useful!