There's a story that the first European settlers in North America were appalled by the gardening techniques of the natives who, instead of planting in neat, homogenous rows, would grow corn, squash, and beans all together in a tangled mess.
I do a bit of both.
Given the limited space in my own backyard garden (I could have double or triple the space and it would still feel limited), I've tended to adopt and adapt "intensive gardening" techniques, in which I plant more closely together than traditionally recommended, and in succession, so as to maximize the harvest from each square foot of soil. The bed in the photo above is a great example.
This three-by-six foot raised bed isn't really big enough for the three winter squash hills within it (acorn, spaghetti, and butternut) let alone the rest of the plantings, yet as you can see it's going gangbusters. At the time I put the squash starts in the ground I sowed the perimeter with four different varieties of lettuce, and the space in between with two varieties of bush beans. Kale and dill also generously volunteered throughout the bed (let one or two dill plants go to seed, and you'll be eating baby dill throughout the next season).
As you can see the bed is beginning to get awfully crowded, with the squash leaves starting to shade out everything but the beans. That's fine. Baby lettuce, kale, and dill salad for dinner tonight it is. As my main crop grows, I gradually thin out (you know, eat) the interlopers. In the late summer, when the beans have played out (bush beans ripen all at once) I'll broadcast kale and mustard seed underneath the squash, some of which will surely survive to give me an overwintered early spring crop. Next summer this bed will host tomatoes.
The bed in the background tells a similar story. While my tomato plants are relatively generously spaced, I've temporarily filled in the gaps with arugula, spinach, basil, parsley, and of course, more volunteer kale and dill.
As you can tell, I love to garden. There's little in life I find more gratifying than growing, eating, and sharing my own food. But if you have the space and the inclination, it can also prove incredibly economical, providing a surprising amount of organic produce for very little cost.