An interestingly simple way for a populous to share it's non-perishable foods would be to utilize what already exists in the majority of large cities, which, coincidentally, seem to harbor the majority of those without homes; Old, no-longer-in-use mailboxes.
Even without modification, these mailboxes could stand to receive foodstuffs from informed passers-by, whose charitable donations would make life a bit easier for those of us with less food security than others. However, there is the glaring issue of distribution to consider. If we simply let everyone retrieve this food, there's the possibility of hoarding, or even the probability that someone who isn't exactly less fortunate might dip into the supply. So, how would we go about distribution?
Well, this could be as simple as coordinating with an existing local or international charity. There are already foodmobiles that make rounds in certain areas, and stopping by these foodboxes with a special key to pick up the donations and transport them to a distribution center wouldn't be terribly difficult. Vandalism isn't too much a worry, as these older mailboxes are quite tough to begin with, and honestly, the charities in question probably wouldn't be opposed to the idea of making the extra rounds to pick the donations up.
It's easy; The boxes are already there, they're no longer in use, the trucks are already there; All that's left is some logistical coordination.