Generally speaking, things you should avoid donating:
Expired items
Opened items or things with other package concerns
Things in glass or cellophane wrappers (they can damage easily in transport)
Things that require refrigeration
Leftovers/prepared foods and baked goods

Your best bet is dry, shelf stable foods.

That being said, always check with your local food bank (or wherever you are donating) on their specific guidelines. Some places have a list of specific expired items they will take and will also usually have strict guidelines as to how expired those items can be. Some food banks also accept baby items, like diapers. And some food banks have programs for accepting fresh produce from your garden or fruit trees. Most food banks also only accept monetary donations in certain formats. For an example, our local food bank actually does accept refrigerated food, frozen food, prepared food, food service items, personal care items, and cleaning products, but does not accept expired food and only accepts monetary donations in the form of gift cards for a specific local grocery store.

Also check your local food bank for a most needed items list. Most have them.

If that's not possible, here is a list of the most commonly requested items at food banks nationwide:
Peanut butter
Canned soups & stews
Boxed meals
Canned fruit
Canned vegetables
Canned proteins such as tuna, salmon, chicken, or SPAM
Canned beans
Pasta
Rice
Cereal
Shelf stable/powdered milk
Pantry stables & cooking essentials such as cooking oil, salt, pepper, spices, flour, sugar, condiments, pasta sauce
Fruit & vegetable juice
Baby formula & baby food
Complete snacks like crackers, apple sauce, dried fruit, nuts, granola bars
Culturally relevant items

I tried to list things by most mentioned to least mentioned, but I feel like pantry stables (and culturally relevant items) get really overlooked. And tuna was the most requested on lists that had canned proteins mentioned individually, that I could see.

A lot of advice sections at the few food bank websites I found that had them also asked that you consider trying to donate canned foods with pop tops/don't require a can opener and the healthiest versions of foods you can, when possible.

I hope this helps.

I don't know who might need this info (which I meant to post the last week of November) and it only applies to USPS.

The current flat rate box prices are:
Large: $52
Medium: $22
Small: $13

Ship by dates for packages to arrive by Dec 25 (according to the USPS):
USPS Ground Advantage: 12/17/25
USPS Prority Mail: 12/18/25
USPS Priority Mail Express: 12/20/25

Postage rates are also scheduled to increase on January 18th. They are not increasing the rate for First class stamps, but instead it will be increased rates for shipping packages.