What can I do with left over egg whites

Thanks evertony for your answers, I'm sure we'll be eating some delicious treats

I just saw this. My go-to is King Arthur Flour's flourless fudge cookies. Easy to make (one bowl and one whisk) and delicious.
http://www.kingarthurflour.com/recipes/flourless-fudge-cookies-recipe

You might want to check out the submissions to the Your Best Recipe with Egg Whites contest (https://food52.com/contests/378-your-best-recipe-with-egg-whites), and this question comes up a lot on the Hotline, so you could look at some old threads on the topic, like https://food52.com/hotline/21661-i-m-making-a-recipe-that-calls-only-for-egg-yolks-about-9-to-be-exact-what-s-the-yummiest-thing-to, https://food52.com/hotline/19301-2-dozen-egg-whites, and https://food52.com/hotline/14097-leftover-egg-whites.

Meringue cookies, macaroons, Baked Alaska!