If I remember anything about 2008, the campaign headquarters people today and tonight and all day tomorrow and probably into the evening are not going to be able to stop for a meal. They are going to be hungry, hungry people!
If you have a campaign office in your vicinity, think food for the volunteers. Perhaps something you can whip together from your own kitchen or something you can pick up at a store and deliver, or even order pizza for them and have it delivered to the office.
Snacks of all sorts; veggie plates with a dip; sandwiches; pretzels; chips and dip; cookies; cake; pie; cold meat plate; potato salad; any salad, hot or cold, soda and juices, and add some plastic forks and paper plates and cups just in case. There is a world of food to be devoured by starving volunteers in between GOTV phone calls and you can provide much needed support even if you can't be there to phone call or drive people to the polls.
Of course, if you can make a few calls while at the office, that won't hurt either.