oh boy an extention here on dannywells answer here leave the kitchen door open as well and heat the hallway up and why not leave the bedroom doors open as well so they get heated up (the bedrooms that is and not the doors)......
dannywells is right in one way, if you leave the door open it will warm a kitchen quickly and you'll feel the benefit, keep the door closed and although the same amount of heat will be put into the kitchen, due to the insulation in the oven it will be over a much longer period and perhaps not be noticed. Of course as rojash says it could be dangerous with kids.