Pumpkin is certainly a superfood for dogs. It provides vitamins, trace minerals and fiber, and can help control digestive problems. Most dogs like it, and some have been known to attack a jack-o-lantern to get it.
Pumpkin Health Benefits
Cooked pumpkin is better for dogs than raw, and pureed pumpkin is easy for them to digest. Pumpkins, like squash (also good for dogs), is high in zinc, iron and beta carotene, which converts to vitamin A. Don't overdo it, though -- vitamin A is fat-soluble and is stored in the liver until needed, so too much can become toxic: go easy on serving any kind of liver and hold the pumpkin when you do. If your dog comes down with diarrhea, add pumpkin puree to his food -- the fiber in it will absorb some of the excess water. If he's constipated, add pumpkin -- the same fiber that eases diarrhea will act as a stool softener.
The Canned Stuff
Canned pumpkin puree is perfectly fine. Get it from the grocery store, but be careful not to pick up pumpkin pie filling by mistake (they're often stocked side-by-side), as this contains way too much sugar and spice to be nice for dogs. If you don't use enough to keep it from going bad before the can is empty (2 to 3 days), put the rest in small containers and freeze until needed -- won't hurt it a bit.
The Homemade Stuff
Homemade pumpkin puree is easy to make and freezes just as well as canned. You can oven-roast, boil, stew or microwave your pumpkin and puree it in your blender or food processor. Skip using the big carved porch decorations, though -- too watery. Buy a smaller pumpkin meant for pies to get maximum return in quantity and quality for your effort.