I don't know if this is happening everywhere, but I have seen in our area that there are at least two stores that are collecting donations for the food bank on a regular basis--at least I saw nothing that indicated a start date and/or end date for the collection. One place is the local national chainstore, where they have a basket of food for $1.00 or under or something to that effect right at the register. They also have a barrel in the entryway (where you pick up your cart if you so desire) where I suppose you could just bring in something to donate before you enter the store if you wanted. (I bet they wouldn't mind if you dropped something in that you bought in the store on the way out, either.... :)
The other place is a dollar store, where the price of the items is pretty much what you would expect. (Just don't forget the sales tax...) The cashier asks you if you want to donate at the register, (as they do at the national chainstore as well) and if the answer is yes, grabs an item from the basket, rings it up, and puts it away to be taken to the food bank.
To me, this indicates the great need that there is when it comes to food bank donations. Specifically in Idaho, you can read about what's happening when it comes to food banks in a couple of articles-- if you are in need of assistance in Coeur d' Alene you can look here, or if you can offer assistance in Pocatello by donating to the food bank, look here. The food drive in Pocatello is in connection with an Extreme Makeover: Home Edition project that will take place there, which I think is a great idea, since they want to help more than just the family that's getting the house.
So, I don't know if this retail-style food donation practice is everywhere, or just around here. In any case, from what I understand, the need for donations is growing, and apparently so are the businesses that are trying to meet the demand...