Today’s featured promo on MacUpdate offers WhatSize for US$5.99 (54% off, retail $12.99). “WhatSize is a simple tool that allows the user to quickly measure the size in bytes of a given folder and all subfolders and files within it. You would be surprised at to how many useless files might be laying around on your hard disks. The files and folders are automatically sorted by size, with the biggest sizes first.” WhatSize requires Mac OS X 10.3.9 or later.