leftover egg whites

This is for next time,cause by now you probably already used those:HomeMadeMarshmallow!Beat the egg whites till they're firm(add a pinch of salt and/or baking powder,they'll get firmer and last longer)and when they begin to spike,pour slowly some syrup(4 to 6 eggs:1 cup water,2cups suggar mixed,boiled on low heat till it thickens,let it cool.)while still beating.But if you're lazy like me and don't feel like using the stove,forget the syrup and use 2 to 3 cups of fine suggar.You can add vanilla or lime zest.I like vanilla better.This will last for 2 days in the fridge,but if you add a table spoon of emulsifier gel,it will last for 4 days and you will get better texture.

You can also use them to make a "raft" to clarify stock, if you happen to be making stock.

Make turron (aka nougat, aka torrone). It's easy and really good. Serious Eats recent has a recipe for Turron de Alicante, which uses marcona almonds, but you can use any kind of almond or pistachios,

http://www.seriouseats.com/recipes/2011/12/dulces-turron-de-alicante-nougat-with-marcona-almonds-recipe.html

Funny - I just posted about having 22 egg yolks and not knowing what to do with them (the whites had been used in angel food cake). Sounds like you and I need to team up! And, BTW, what was the ice cream recipe that used so many yolks? (maybe I could use that...) ;)

you can use them to roast nuts instead of oil

Meringues!

Angel food cake.

As @Louisa says, they freeze well. They can also stay in a clean sealed container in your fridge for a good couple weeks - once the whites start to look cloudy throw them out.

You can also freeze them.

I usually just save them for the next day and scramble them into a larger batch of whole eggs with some cream to make up for the lost richness.