Another recommendation for Angel Food Ministries! They provide healthy, and fresh, food at an incredible price - and they have no income limitations, so you don't have to justify why you are using their service. They provide food at cost - so you are not taking resources away from other people when you use them.
Do you have a bakery outlet in your area? That's a great way to stock up on whole wheat bread, and store it in the freezer.
I don't buy processed stuff with unhealthy ingredients. That is the one decision that's saved us the most money, and freed up dollars for healthy food. For the price of one package of cookies, I can buy a bag of apples (and they keep well for a long time in the frig.)
Seasonal fruit and vegetables tend to be a bargain. We eat them when they are in season. We almost always have bananas and iceberg lettuce in the house, because they're generally inexpensive.
A whole chicken bought on sale is a bargain, and can be used for several meals. Roast in the oven (I often do 2 at a time) or even in the crockpot.
I agree about frozen and canned vegetables - tests have shown them to be as healthy as fresh (in some cases, more so, because they're picked and processed immediately after harvesting).
Fruit juice may cost more than colas - I don't really know. It's kind of irrelevant, because colas aren't food, and fruit juice is. In our house, they aren't in competition with each other. I buy healthy food first, and only buy the luxuries (like diet cola) if there is money left over.