Freeze gallon jugs of water and place them in your cooler. They'll keep your food cold, and you'll have plenty of water to drink for later.Other things you can freeze to use for later: pasta sauces, chili, and pesto.
Portable recycling/trash Bag Holder : perfect for BBQ's, camping, parties, etc. and for recycling too! I would probably keep it away from the food table though, but I like how it doesn't take up much space for packing on a trip!