While I try to do the weekly planning, I also keep my eyes open for "reduced for quick sale" produce and meat/fish to supplement our usual weekly supply of fresh produce with the also-rans.

If you can eat these items first, or process them for later consumption, you can stock your pantry/fridge/freezer and continue to build up items for use. For example, I buy up a couple of packages of overripe bananas every month, then peel and freeze them (I also do this routinely with the bananas we don't eat fast enough in the summer, when they ripen quickly). These are either added to smoothies, or pureed/smashed with a fork for addition to quick breads or pancakes. I also buy quantities of mangoes when they are on sale, and make Crockpot mango-ginger chutney for curries and as a side dish or addition to rice. This lasts forever in the fridge, but can also be canned.

Peppers can be roasted (remove any funky spots first), and then skinned and preserved in olive or other oil. They are also very nice as a puree or added to a sauce. Buying roasted red peppers in oil (with whole garlic cloves) is an expensive proposition. These also make lovely gifts for people (a la Mason jar gifts).