You can save a lot of money simply by eating produce that is in season. Yes, you may want strawberries in November (I always do), but you'll have to pay 4 times as much for them as you would buying them in season. Eating fruits and veggies that are in season is not only a great way to save money, but it also give you a great variety to your diet. If you eat apples and bananas year round, you're missing out on all the nutrients that the other fruits provide.
A lot of these are available at good prices longer than their standard season. And some are readily available all year long (thanks to modern farming). But, this give you a good idea of when you will be able to get great deals on your fruits and veggies.
Spring
Apricots
Artichoke
Asparagus
Avocado
Chives
Collard Greens
Fava Beans
Fennel
Mango
Mustard Greens
New Potatoes
Papaya
Pineapple
Rhubarb
Shallots
Spinach
Strawberries
Sugar Snap Peas
Snow Peas
Vidalia Onion
Watercress
Summer
Beets
Blackberries
Blueberries
Broccoli
Cantaloupe
Cherries
Chinese Cabbage
Corn
Cucumber
Eggplant
Green Beans
Nectarines
Peaches
Peppers
Plums
Raspberries
Summer Squash
Tomatoes
Watermelon
Zucchini
Fall
Acorn Squash
Apples
Belgian Endive
Brussell Sprouts
Butternut Squash
Cauliflower
Carrots
Celeriac
Cranberries
Figs
Garlic
Ginger
Grapes
Mushrooms
Parsnips
Pears
Pomegranate
Pumpkin
Sweet Potatoes
Swiss Chard
Winter
Chestnuts
Grapefruit
Kale
Leeks
Lemons
Oranges
Persimmons
Radicchio
Radishes
Rutabaga
Tangerines
Turnips