From Martha Stewart. The best one I've found.
1 cup flour
2 tablespoons sugar
1 teaspoon baking powder
1/4 teaspoon salt
1 cup milk
2 eggs
4 tablespoons melted butter
Combine the dry ingredients in a bowl, and the wet ingredients in another bowl. Mix them together without beating out all the lumps. Bake in your waffle iron.
A lot of waffle recipes call for adding whipped egg whites to the batter, which is more trouble, but this comes out just fine without that extra step.