Any food can be frozen, but there are some foods that freeze well and some that don't. It's going to take some experimentation on your part to determine the foods you're willing to freeze because taste and quality is highly subjective and you may be willing to accept changes to the food that other people find unacceptable.
If there's a certain type of food you're wondering about, the best way to find out whether it works as a freezer meal is to try it yourself. Making extra and putting it in the freezer for a week or two before eating it is the only way to find out for sure whether you're going to like something or not. I've found some of my favorite freezer meals this way and I've been surprised more than once when ingredients other sources said shouldn't be frozen turned out just fine when I tried freezing them.
Now, having said that, I can definitively say there are some foods that lend themselves well to being frozen and others that don't do so well in the freezer. Let's take a closer look at some of the foods that freeze well:
Eggs are a strange item, in that cooked eggs don't do well when frozen and tend to turn rubbery, but uncooked egg can be cracked into a container and whisked together and they freeze just fine. Fill an ice cube tray with whisked eggs and you'll have little cubes of whisked egg that can easily be added to recipes. Each cube is approximately 1 egg.
Egg-white based toppings like meringue turn rubbery when frozen. Make meringue frosting the day you plan on eating the item being frosted for best results.
If you'd like, you can separate the whites from the yolks and freeze them individually. Add half a teaspoon of salt to the whites for every 5 eggs you're freezing. You don't have to add anything to the yolks.
Meat & Poultry
Most raw meats can be frozen, but it's important to make sure you package them correctly before tossing them in the freezer. Supermarket packaging allows air to reach the meats, so it's important you repackage any meats you plan on keeping in the freezer for more than a month. Failure to prevent air from reaching the meat will result in freezer burn and rapid degradation in the quality of the meat.
The best packaging for the freezer is any packaging that prevents air from reaching the meat. Vacuum-packing works best, followed by wrapping the meat in plastic wrap or freezer paper and placing it in an airtight freezer bag. Remove as much air as possible from the bag before sealing it and placing it in the freezer.
Don't cook meat before freezing it unless it's part of a freezer meal. If you want to store marinated meats, make the marinade, put it in a freezer bag with meat and freeze the meat.
Poultry can either be frozen whole or cut into pieces and frozen. Package poultry the same way you would package other meats. Don't stuff whole birds prior to freezing them. Wait until the day you plan on cooking them to stuff them.
Fish (and most other types of seafood) can be frozen, but it's important to get them into the freezer while they're still fresh. Try to freeze fish within a day or two of purchasing it or catching it. Frozen fish is highly susceptible to freezer burn, so be sure to package fish in a manner that keeps air from reaching the fish.
Glazing is a technique that can be used to help ensure fish stays fresh. Freeze a piece of fish and then dip it in extremely cold water and freeze it again. Continue dipping and freezing the fish until the fish is coated in a layer of ice. Glazed fish tends to stay fresher than fish that hasn't been glazed.
Vegetables are a great item to buy in bulk while they're in-season and toss in the freezer. Most vegetables have to be blanched prior to freezing them. Here's a link to more information on blanching vegetables:
Most varieties of fruit can be frozen, but will get a bit soggy when they're thawed out. Frozen fruit doesn't lend itself well to being eaten on it's own once thawed, but it will work just fine for smoothies. Don't wait until the fruit is starting to go bad to freeze it. Freezing fruit definitely isn't going to improve the quality of the fruit.
Soups & Stews
Most soups and stews can be frozen to good effect. Some do better when assembled and frozen prior to cooking them, while others do best when they're cooked before you freeze them. Experiment with your favorite soups and stews to figure out what works best for you.
I've found that soups and stews that use flour or corn starch as thickening agents don't freeze well when the flour or cornstarch is added prior to freezing. They thicken up much better when the flour or cornstarch is added while they're being cooked or reheated on the day I plan on eating them.
Bread and Baked Goods
A number of breads and baked goods can be frozen and then thawed out on the day you want to eat them. You can cook the bread or baked goods first and put them in the freezer or you can make the dough and freeze it before you cook it. It's important to make sure dough is completely thawed out before attempting to cook it or the results can be unpredictable.
You won't see dairy products on many lists of foods that freeze well.
I'm including it here, with a few reservations. Certain dairy products do much better when frozen than others. Cheese will often turn crumbly when frozen, but freezes fine when used as an ingredient in most freezer meals. Shredded cheese can be frozen and won't suffer too much of a hit to quality when used to top cooked foods.
Foods that use dairy products like milk and cream as an ingredient are usually able to be frozen, but the diary may start to separate. This isn't a problem for foods that can be stirred back together, but may be more problematic when the dairy is used in whipped toppings and other items that can't be stirred.