I've had outstanding luck with "Ova-Easy" whole powdered eggs. The product is dead easy to use and for the life of me I can't tell any difference. It comes in a plastic package that can be resealed and unopened will last a long time.
As far as leaving the egg out of some recipes; it was explained to me that most times in cake sorts of mixes there is baking powder that provides a gas to expand the flour into a lighter form but the eggs are needed to denature (cook) and fix the loft in place. You know when you look at an uncooked egg the thing is a slippery slimey thing, but cook it and it becomes more or less firm. Well, imagine the cake batter cooking; as the gas heats and expands at the same time the egg is cooking and as it does it's structure will hold the shape of the gas bubble long after the cake has cooled and the gas is long gone. The other option is to eat your cake in a form something like flat bread, which isn't the worst thing that ever happened in the world.
Just say'n....
Best Wishes, Rob