Leftovers won't actually be leftovers if you thought of blessing someone with it before it became a waste. Some people prefer hoarding things than thinking that someone somewhere might not have been able to afford this or might be in a dare need of it or even think of blessing someone with it.
When anyone hears the word leftovers I know the first thing that would come to mind is food but in this context it is beyond food. Whatever you have in your house that you don't use often or you have even forgotten you have it, has become a leftover to you . Why not look for someone that such thing can be useful to and bless the person with it. I tell you in every home there is a useful leftover. Stop hoarding things and letting them waste. Check for the nearest home ,it could also be someone not too close to you and bless them with those cloths ,shoes ,bags ,home gadgets,utensils and food items . Whatever you see and know is still ok for use but is not useful to you again or hasn't been useful to you in a long time is a useful left over. The fact that they are called leftovers doesn't mean that what you are giving out should be totally useless. It simply means that you either have them in two or more, things that you don't seem to have fleer for again (happens most time in fashion), things that are no more useful in your house. If you check around you, someone who can't afford them is in dare need of it.
The first step to making your leftovers useful is to develop a giving habit, because sometimes getting too attached to things can deprive you from letting go or giving out. You also have to constantly do decluttering (cleaning, reorganizing and giving out) every 2-6 months. Decluttering is not the normal cleaning you do most times on weekend but it's for the purpose of reorganizing and giving out those things you aren't in need of. Doing decluttering especially for a large house could be very tasking so it's good you do it for one part of the house at a time.
In summary your leftover is useful to someone so learn to give, learn to be a blessing, throw kindness everywhere. Your reward is not in man but it's in God!