I came across this recipe when I was looking online for recipes specifically using sausage.  I got it from Simply Recipes.

Sausage, Spinach, Ricotta Stuffed Pasta Shells

12-ounce package jumbo pasta shells
1 Tbsp olive oil
1 cup finely chopped yellow onion
1 pound sweet Italian sausage, casings removed (I used ground HOT sausage)
1 Tbsp minced garlic
1 large egg
16-ounces ricotta cheese
10-ounces chopped frozen spinach, thawed, squeezed dry, chopped further
1 cup grated Parmesan cheese
1 Tbsp chopped fresh basil or 1 teaspoon dried basil
1/4 cup unseasoned bread crumbs
1/2 teaspoon salt
1/2 teaspoon ground black pepper
28 ounce can tomatoes with herbs, including liquid, tomatoes broken up (or your favorite tomato or pasta sauce)
shalllow baking dishes

Bring a large pot of salted water to a boil (1 teaspoon salt per quart of water).  Cook the pasta shells according to the instructions on the package.  Drain, rinse in cold water, and set aside.  Heat olive oil in a large skillet on medium high heat.  Add the onions and cook until softened, about 5 minutes.  Add the sausage to the pan, breaking up the sausage into smaller bits.  Cook sausage until cooked through, and no pink remains, about 5 minutes.  Add the garlic and cook until fragrant, about 30 seconds to a minute more.  Remove pan from heat.  Beat the egg slightly in a large bowl.  Mix in the ricotta, chopped spinach, 1/2 cup of the Parmesan cheese, basil, bread crumbs, salt, pepper, and sausage mixture.  Fill each cooked pasta shell with some of the ricotta, spinach, sausage mixture.  Spread 1/2 cup chopped canned tomatoes over the bottom of the baking dish.  Arrange the stuff pasta shells in the dishes.  Spread the remaining tomatoes over the top of the pasta shells.  At this point you can make ahead, to freeze (up to four months) or refrigerate before cooking.  (If freezing, cover with foil, then wrap with plastic wrap.)  Heat over to 375 degrees.  Cover the pan with foil and bake for 30 minutes, until hot and bubbling.  Remove foil and sprinkle with remaining Parmesan cheese, bake uncovered for 10 more minutes.