The quick way to soften butter for baking, with a little wax paper and a rolling pin.
Just put the stick of butter between two large pieces of wax paper. Using a rolling pin, press down on the butter. Roll it out they way you would roll out a pie crust. When the butter is about 1/8 to 1/4-inch thick, lift off the wax paper and peel away the butter (before it gets too soft to peel).
Voilà! Softened butter, ready for beating.