As someone extensively involved, as variously an advocate, a volunteer, and a board member at all levels of this "food chain" (pantry, GCFD, America's Second Harvest network of food banks) I feel I need to chime in.
The claim that $ is more valuable than food is both right and wrong. On the national level, America's Second Harvest can procure 20 pounds of food for every $1 donated. This is how they're able to distribute nearly 2 BILLION pounds of food annually on a budget of less than $40 million. On a slightly smaller scale, this is what the GCFD does as well. Your dollar will indeed go farther at either one of these organizations than it ever will at a grocery store.
It's a little more complicated at the micro-level, where, as one poster pointed out, there is greater concern about providing well-rounded, nutritious meals, rather than simply "enough food." Oversimplifying the process a bit, pantries can "buy" food from GCFD at $0.07/lb. Again, a dollar will go farther here than it will at a grocery store. Additionally, a financial donation allows the pantry to use the money where it is needed most. Perhaps with the terrible cold they need to spend more on heat, perhaps with the rise in gas costs they need more so that they can get to GCFD or make deliveries to disabled or elderly clients. Financial donations will enable them to be the most efficient.
On the other hand, pantries also have "gaps" that they need to fill, items that are difficult to come by from GCFD because of high demand or lack of donations from major food manufacturers. This is where food donations can be extremely helpful.
They are only helpful if you contact the pantry to see what they are in need of, and bring items that specifically meet this need!
These items typically include:
Peanut Butter
Jelly
Tuna
Personal hygiene items (deodorant, toothpaste, toothbrushes, shampoo, soap)
Baby food
Diapers
Mac & cheese
Soup
To put it more broadly, pantries need sources of protein. They need stuff for babies, which is often in extremely short supply. They need foods that picky eaters will like and that are shelf-stable.
Items pantries do NOT need and do NOT want:
1) Weird foods that you're cleaning out of your pantry (you know, those 'gourmet' items with odd flavor combinations). When clients have a choice over what food they get - and most pantries attempt to give them some control over what they get - they do NOT want quinoa. They do not want beet jelly. They do not want capers. Nothing wrong with any of these items, but if you donate them to a pantry, they WILL sit on the shelves, take up space, and end up being a bigger hassle to get rid of.
2) Anything expired/dented/rusty/home canned. Pantries cannot take these items. They are not safe, you are simply passing on the task of getting rid of them to an organization that could better use its time and resources doing other things.
3) Anything glass. If it breaks, that's another mess they have to clean up, and it can potentially ruin other items.
4) Cans upon cans of baked beans, or other very cheap items that people tend to buy in bulk for food drives. Think of what you would like to get, if you were dependent on a pantry for sustenance. Plus these are the items they are most likely to be able to get from GCFD or other sources.