Softened Butter

I often make recipes (like cakes) that call for softened butter. Of course, I rarely plan ahead so I need a way to soften the butter quickly without melting it. My favorite method is to slice the butter into about 1/4 inch slices (1 tablespoon or a little less each). I sometimes turn the oven on for a minute then turn it off, open it and put the plate of sliced butter in the open oven. I leave it there, for a few minutes (with the door still open), and it's ready.