[ETA: I already love this thread.]
Soup is one of the greatest inventions ever, and such a great way to save/not lose money. One of my faves to make is what we call green soup. It's a real non-recipe recipe.
Take whatever (primarily above-ground) vegetables you have on hand, especially frozen scraps or produce past its prime. This is a great way to use up those bits of veg that aren't enough to make a meal, fresh produce that has softened (but isn't slimy), even bits of leftover takeout. E.g., I may end up using green beans, broccoli and cauliflower stems, red/yellow/orange peppers, leftover bits of onion, stems from various greens collected through the months, a sad tomato, maybe a couple of wayward carrots or celery, a zucchini, a few mushrooms, and some steamed water chestnuts, snow peas, and cabbage from the nearby Chinese delivery place. Whatever bits and bobs are around.
Add in a bag of fresh or frozen greens, such as spinach, kale, or collards. (I avoid beet and carrot greens, though, as they tend to take over flavor-wise.)
Toss all in a pot and add broth (say, chicken, veg, or ham) or water + bouillon to about 3/4 of the height of the veg (or more liquid if you like your soup thinner), and add whatever spices you like. I usually do at least garlic and lemon pepper, and sometimes curry powder. Sometimes I'll add ginger and fish or soy sauce.
Boil the hell out of everything, until the hardest of veg (say, carrots) can be easily pierced with a fork.
Puree. (I use a stick blender.)
Adjust seasonings, add more broth if you it's thicker than you like, maybe add some lemon juice or a splash of vinegar for brightness, and you're done. For a silkier, richer soup, melt in some fat (e.g., butter, bacon fat, olive oil).
Makes a great snack or light meal on its own or with interesting add-ons, such as pecans or walnuts or almonds, crumbled bacon, sour cream, and/or green onions. Can also be used as a base to which you add, say, chicken and couscous or ham and rice.
It's pretty foolproof, and such a great way to get a solid shot of vegetables into your day. As mentioned, I avoid beet and carrot greens, as well as beets in general, as they all tend to overpower the other vegetables. I don't avoid cabbage because I really like it, but it, too, can tend to overpower, so I wouldn't make it the predominate veg. If the vegs you have on hand tend toward the bitter end, you can throw in an apple or orange when you're boiling the veg to temper some of the bitterness. (If you find it bitter after having already boiled and pureed, throw said fruit into the microwave to soften, puree, then incorporate into soup.)