For those who need to clear up some hard drive space, figuring out which files are both large and unnecessary can be a challenge in Mac OS X. GrandPerspective is a very helpful free utility. It displays the contents of any folder you like, including your entire drive, as an image where blocks appear for each file proportional to the disk space they occupy. Within minutes of launching it, I discovered that (in an ancient backup from my old PC), I had disc images for three different archaic versions of Linux eating up 700 megabytes each.
In any case, it seems like a useful piece of software for anyone trying to manage the hard drive space on their Mac.