In a large skillet cook the sausage, onion, and garlic until meat is brown. Drain off fat.
In a 3-1/2- or 4-quart crockery cooker combine spaghetti sauce, mushrooms, pepperoni or Canadian-style bacon, and basil or oregano. Stir in the meat mixture.
Cover; cook on low-heat setting for 3 hours. If desired, stir in ripe olives and sweet pepper. Cover; cook on low-heat setting for 15 minutes more. To serve, spear the dippers with fondue forks and dip into the fondue. Makes 10 servings (about 5-1/2 cups).