Preheat the oven to 350° F. In a large pot of boiling salted water, cook the ziti until just barely tender; drain and place in a large bowl. Mix the ricotta cheese and half of the mozzarella cheese with the ziti. Grease a 9" X 13" baking pan; cover the bottom of pan with half the spaghetti sauce. Spoon the ziti mixture into the pan; cover with the remaining spaghetti sauce. Sprinkle with the Parmesan cheese and top with the remaining mozzarella cheese. Bake for 20 to 30 minutes, or until cheese melts and is lightly golden.