Shredded or sliced Cheddar, Swiss Mozzarella, Gouda, Provolone, or other firm cheese
Cottage, ricotta or cream cheese
Cooked, drained and crumbled sausage, bacon or ground beef
Flaked canned or cooked fish
Sauteed sliced mushrooms
Sauteed chopped onions or green pepper
Drained, cooked, chopped, diced or sliced vegetables
Drained, canned or chopped or sliced fresh fruit
Chopped nuts
Jelly, jam or preserves