Our town's pantry is in the church where I work. The needs flucuate SO much. They'll go through spats where they need protein items (peanut butter, tuna, canned meats....) desparately. Currently they are completely overflowing in tuna. Similar cycles gone through with spaghetti and sauce. It's (pardon the pun) usually feast or famine. Ours gets constant donations of canned corn and peas... but those are often the things going out just as fast....
Point being- if you know where the food will go, I'd give them a quick call and ask.

If not- they'll likely to be able to use any canned/boxed food stuff you leave for them! It's sad how much more use our pantry has seen this year. I know they are grateful for any and all donations!
The two things they consistantly do not want are cranberry sauce and canned pumpkin. These get donated in excess around Thanksgiving time and extras just sit around taking up space the rest of the year.
General recommendations I'd offer from the "trends" at work- they try to encourage healthier foods (eg cheerios over Fruit Loops, healthier snacks such as pretzels vs potato chips...) BUT "health foods" or "exotic" ones tend not to get taken. The users are looking for familiar things that they know how to cook/know they will like since they are limited in the amount they can take each visit.
Things often not donated- breakfast cereals, health/beauty products (toothpaste, shampoo...), laundy detergent (this is a biggie, more people tend to donate alot of small items vs $5 bottles of detergent...), formula, diapers and things kids can take to school for snacks.
PS most definitely does not need to fit in the bag they left! When we do our scout food drives, we actually end up repacking everything in boxes as soon as we pick it up anyway. If you have a lot and an empty box, I'd put it in there. But more then the bag- defintely will be welcome!
