If spring cleaning season has come to your neighborhood, nothing will give you better incentive for grabbing a mop and feather duster than opening the drapes and letting the sunshine in. Those bright beams will start you thinking about grilling parties and other fun outdoor activities. They'll also reveal colossal dust motes that'll look like a cosmic indictment of your cleaning prowess. When the skies are overcast, living in a cozy cave under a quilt is comforting. When the windows are open and the sun is streaming in, though, dusty furniture and dirty carpet look downright nasty. Those sunny slices of dusty air are a wakeup call if ever there was one.