For the Seattle Bake Sale for Share Our Strength last weekend I made blueberry cobbler baked in half-pint jars. I found the jars to be fantastic for bake sale purposes and would work splendidly for picnics as well. I think using larger jars (pint sized) for bigger portions would work out just as well.
Since the jars themselves they looked strange (like I was selling jam, maybe?) I created labels printed on cardstock and cut to fit nicely between the layers of the screw on lids. On the back of the labels I put suggestions on other things to do with the jars, things we use them for are storing seeds from annuals, shaking vinegrette dressing and sipping bourbon from them.
Click for the recipe for cobbler baked in jars, including tips on dividing into two dozen portions.