This video features Hunt, Gather, Cook author Hank Shaw demonstrating how to gut a duck, saving the wings, gizzard, heart and liver, as well as the feet (for stock) and fat (for rendering). To see the "How to Pluck a Duck" video, go here.
If you have sea ducks or other waterfowl that have an off taste, try skinning them - the flavor (and aroma) lives in the fat and skin. The skinning video is here.
And yes, I know it's easier to breast out your ducks, but you're wasting half the meat when you do that. Want proof? Read this.