Mini-Pumpkins are used primarily for decoration during the Autumn months. You can however, cut the tops off, and par bake and use for soup containers~pumpkin soup....they were developed in California and come in various sizes and colors from light yellow, to deep yellow, to green stripped, to white. 

Here are a couple of mini-pumpkin websites:
http://www.kanservu.ca/~whalls/pumpkin.htm

http://www.pathfinder.com/FoodWine/box/roastpump.html

http://www.ksl.com/TV/recipes/files/1028mini.htm