Baking soda is great in ovens.
Mix up a cup of backing soda and water, paint the paste onto the walls of the oven and it hardens like a furnace lining. Any little baking incidents will stick to the coating and once a year you just brush it off.

You can also pour a box of baking powder in the bottom of the oven - it will absorb any spills. When it gets too gross just sweep out and replace.

Never clean an oven again !