Do you have any friends/family that have a Costco membership, or similar type bulk store? Best things I buy there are cottage cheese, eggs, chicken breasts, ground turkey, apples, etc. If you have a freezer, as someone else mentioned, buy in bulk and freeze.
If you're going to your local supermarket, shop around the outside edges of the store, as that's where the healthier products tend to be (meats, veggies, dairy, etc).
One thing I've found that is great for making wraps or whatever, are LaTortilla Factory low carb/high fiber/protein whole wheat tortilla's. They taste pretty damn good, are great for you and low in cal. and are pretty cheap too.
Try cooking brown rice with chicken broth instead of Ramen, it's much better for you and will taste about the same. As others have said, lots of veggies, frozen or fresh depending on how fast you would eat them, russet potatoes (just read an article that says that russets are more nutrient dense than baby reds, etc). I always keep a tub of the organic greens handy, $4 at Costco and it'll last you a week or so, toss in some fresh broccoli or whatever and you have a healthy and filling salad.
Basically just learn to shop smartly, avoid anything with high fructose corn syrup or hydrogenated oils, try not to buy/eat anything "white" (bread, rice, etc). You may pay a bit more, but it will also satisfy your hunger and sate you for longer than something cheaper.