Muscadines, or "scuppernongs" as I've also heard them called (by my grandaddy) are in season at the end of summer, and I've always thought of them as the heralds of what passes, in South Mississippi, as "fall."
Down here "fall" should just be called "slightly less miserable summer."
I don't know many people who do much with muscadines, because although they taste great, they're not as easy to eat raw as grocery store variety grapes. They have VERY tough skins, pulpy innards, and large seeds. Fortunately, when you cook them down, smoosh out the seeds, and then bake them between two flaky layers of pie dough, they soften up considerably, and have a wonderful and unique flavor. This recipe comes from Nancie McDermott's Southern Pies, and the only adjustment I've made is to cut back on the sugar somewhat. Muscadines--or at least, my muscadines--are so sweet on their own that too much sugar actually harms rather than helps the flavor of the pie.
I recommend you add sugar slowly, and taste the filling as you go, until you get it how you like.