The most inexpensive way to obtain produce, hands down, is to grow your own. Planting a garden isn't for everyone -- for starters, you need enough space -- but it can be an immensely satisfying project. You'll gain a new appreciation for and connection to your food, and you'll be amazed at how much better home-grown produce tastes than the store-bought stuff. And did we mention it's cheap?
If you're not sure where to begin your garden, start with herbs like basil, rosemary, thyme and oregano. All these easily grow in pots that can be transplanted to the ground -- or kept in the pot if you decide a garden isn't for you.