When you're making quick breads and muffins (corn, zucchini and banana bread, for example) you can use frozen egg substitute: one-fourth cup of egg substitute is equal to one egg. You won't get exactly the same result, because the fat in a whole egg contributes to a moist, tender texture.
When eggs are used to help make a cake or dessert (like souffle) rise, the egg white does most of the work. If your issue is with the yolk and not the white, you're in luck. Just be sure to use fresh egg whites, which whip (and incorporate air), while egg substitute does not.