Add fresh basil; add diced courgette at the time you fry the onion, or use celery. Add some peas when you put in the tomatoes; add some diced smokey bacon, fried first with no oil to get a crispy result
Add a splash of white wine, or red wine. add a little spinach and pine nuts; add sliced black olives, add sliced mushrooms.
Hope that helps . . .don't add all the above to one sauce by the way. The sauce should never really take longer than the pasta to cook.