I joked once that "frittata" was Italian for "leftover user-upper." Bad joke, but these things really are useful for using up all the little tidbits you have leftover from other meals.
In this pic, a leftover special:
Leftovers from two salads (spinach and mixed greens)
Leftover frozen chopped onions
Leftover fat-free shredded cheese
Cool thing is, I didn't really have much of these ingredients left for a full meal, but combine them with eggs, FF sour cream, etc. and you have an amazing couple of meals that people think came from a specific recipe.