The GrandPerspective 0.9.12.1 update was releaesd on June 14. This Open Source utility for Mac OS X displays a graphical representation of file space use on a Mac. It seemed a bit sluggish on a Core 2 Duo iMac. It seems better suited to looking at specific folders rather than an entire large disk based on my experience. That aside, it is a very useful tool for checking for files hogging space on your Mac.