I'm about to make coconut macaroons! With my leftovers.
Yum.

If you have made a cake batter that seems too heavy, you can whip one or two and fold them in to the batter to lighten it.

Go ahead and use them in some cocktails or if that's not your thing try a some baking recipes, like the suggested angel food cake.

Thanks. I think I am going to use some for marshmallows, and probably use up some miso I have for an egg drop type deal. Thanks aargersi.

Egg whites will last for at least a week in the fridge -- they also freeze beautifully. I use egg whites in meringues and all the variations -- straight meringues, french macarons, pavlova (a New Zealand dessert that consists of a big meringue shell topped with whipped cream and fresh fruit), meringue toppings for pies, or bread pudding. You can also use them in angel food or sponge cakes.

A few days - I eat them for breakfast. On the days I am trying to eat healthy ... on the other days I would probably try a pavolva or something like that ... you could also swirl them into some miso soup for a sore of egg-drop type deal, or scramble them into some fried rice