Though it takes some time to accumulate the necessary egg whites in my freezer, once I've got a good reserve I always turn to angel food cake. This cake can be made a few days in advance of your next party, and it freezes extraordinarily well, so you've really got no excuse for not making one post-haste.
Though I doubted their usefulness in my high school physics class, formulas turned out to be eminently useful in the kitchen. Here's my cake formula, it's something I've used without fail for years now. I love how customizable it is, any flavor you dream can fit into its confines. Enjoy!
When looking for a last minute dessert, these amaretti routinely top my list. I always have some extra egg whites in the freezer, and whipping up a batch of these couldn't be easier.