Saute mushrooms in olive oil (or vegan margarine). Throw in the cooked spaghetti, mix, add soy sauce to taste.
This recipe doesn't have much to it, but sometimes I want something extremely simple.. Sometimes your taste buds can't handle so much extravagance. =) Very tasty, very quick, great when you are in a hurry!
Also, if you have cooked plain spaghetti leftovers, you can use it for this recipe instead of wasting it.