From a chemical perspective, freezing tends to break down the structure of the food, making it mushy. As water freezes, the ice crystals expand, which tends to break down cell walls. So crispy vegetables or delicate fruit will tend to come out soggy - think of the difference between a fresh strawberry and a thawed one.
When I freeze sauces and soups, I tend to chop things like celery and mushrooms fairly finely, so the difference in texture doesn't matter much. Pureed and roasted vegetables freeze well. I will often make pureed vegetable soups and they freeze and thaw beautifully (broccoli, carrot, cauliflower, asparagus, pumpkin, squash, etc). I don't generally freeze milk based soups (like chowders), because the texture goes downhill.
I avoid freezing potatoes, and I don't freeze pasta unless it's filled (it's so easy to cook the pasta while I thaw the other stuff). I do batch make and freeze lasagna, tortellini, ravioli and gyoza. Rice and beans freeze beautifully, although I don't freeze Chinese fried rice with egg.
Spaghetti sauce freezes well, as does chili and stews (without potatoes). Pesto freezes well - it's usually recommended that you add the cheese after thawing. A lot of curries freezes well, particularly tomato based ones. I've frozen coconut milk based curries (Thai, for example) with good effect, although the oil tends to separate out a bit. Shredded pork type dishes freeze well too.
One trick I used a lot when single was to pre-freeze meat. You can saute whole chicken breasts, freeze them, and use them thawed to toss on pasta, or in a salad, or sliced in a sandwich. You can also pre-cook things like ham (or simply slice smoked hams into single serving packages). When I make things like sausage patties or crab cakes, it's easy to make extra and freeze the rest. I also pre-cook and freeze beef shanks, because they take two hours to cook but are great in stews and curries.
Simple steamed vegetables can freeze well, though at that point it's easier and cheaper just to buy frozen vegetables.
