I once read this books called Life As We Knew It. Basically, the moon gets knocked out of orbit, and nature gets smurfed up.

From that I learned:
You can never have too much bottled water, but don't waste it during the winter when you have snow or rain.
Progresso soup--it doesn't require water to cook.
Canned veggies
Don't waste time on perishables
Buy as many blankets as possible. You're probably going to lose electricity, so be prepared for some cold days and nights come winter.
BATTERIES
Matches and lighters are like, super important
And don't ever let anyone know you're still alive