I did a piece for Sustainablog back in the fall about how the food pantries in the US had seen a jump in people who needed their help. I can only imagine that since last fall the need has become greater. In fact, the 2008 statistics for food insecurity (based on 2007 numbers) revealed that 36.2 million Americans, including 12.4 million children, are in danger of being hungry on any given day.
A lot of people aren't able to participate in today's National Day of Service because they have to go to work. And they are thankful that they have a job to go to at this point. If you are one of those people, but you'd still like to do something, why not stop by your local grocery store this evening after work and pick up some food to donate to a local food pantry. I don't think it matters if you can't get the food to the pantry today. Just get it there as soon as you can.