In my attempt to stop throwing away so much produce, I have started freezing chopped onions. Now it's a time saver and huge convenience.
One time I had three huge onions that I wasn't going to use any time soon and that were going to get thrown away. I chopped them all up at once, put in freezer bags, and froze them for later. I LOVE HAVING THEM! I get sick of chopping onions and if it's the only thing I have to chop for a recipe, it's an even bigger drag. Now, I can just grab some out of the freezer and plop right into my pan. Of course, some recipes you have to use fresh, but man -- I really like having them in there. Like, the other day, I made taco soup. Already the easiest recipe, right? With frozen onions, it's even easier.
If I'm chopping a fresh one for a recipe, I go ahead and chop another one at the same time to freeze. Or if I only need half of an onion for a recipe and know I won't be using the other half soon, I just chop up the whole thing and throw the other half in the freezer.