I live in Boston, MA and we have a business here called Fair Foods and what they do is take food that the grocery stores can't sell and they sell it for two dollars for a very full grocery bag.
One of their drop offs is down the street from me and I try to go every week to see what they have available. This last week I got a bag with new potatoes, a bunch of onions, a bunch of bananas, and a big bag of mixed greens. Often times you can buy bulk items: cases of tomatoes, green beans, bags of onions, clementines, etc.
Because a lot of this food hasn't been refrigerated it is ready to eat when I get it. But who can eat a bag of onions! So I will cut up the onions to freeze, blanch green beans and freeze, or can tomatoes for example.
I mostly like to dice my onions but you could slice them in long strings if, say, you did a lot of stir fry.
You can also see some of the bananas I got. My daughter loves them so we generally get through them in time however this week was a little much. So a double batch of banana bread was made.
The other thing I like to do is save soy sauce packets. No I don't need to, but I don't like to waste either. So into my fridge bottle they go. These four packets only came to about 1/8 of a cup but I will get handfuls with my takeout and it does add up.