In the spirit of Sunday's Sale, I've cut out enough fabric for a stack of Casserole/Pie carriers from the Fall '09 issue of Stitch Magazine. Full Disclosure: I wrote this pattern for the magazine, so I'm a little partial to the design. Still, I think it makes a great addition to picnic season. Ours fit snugly around several sizes of casserole dishes, keeping the food warm and the lids in place until we make it to where we're going.
Have you checked out Insul-Bright? I always have some on hand to use for pot holders/mitts, coasters, lining bags that need to keep things cool/hot... it's easy to use and very effective. We have it by the yard for less than 5 dollars/yard. I like to use it for the bottom layer for this project. A word of caution: if you don't want to make any sort of new friends, you may want to avoid this project all together. People get awfully chummy when you pull out an intact casserole full of chocolate trifle or a plate of warm apple pie.