The Donut Ghost House is the first ghost house in Super Mario World, excluding secret levels. To complete the House you have to go all the way to your right and take the door. Once on the other side, keep heading left and take the next door. Hit the yellow block and a P-Switch will pop out. Press it, but don't take the silver door that will appear. Wit there until the Switch times out and then take the door again. Hit the yellow block and this time a vine will pop out. Take it and you'll find the exit.
There is a secret exit at the beginning of the level that you must fly up to at the far left top that will take you to the alternate exit. This alternate exit will open the path to the Top Secret Area.