Since Roshambo commented that WinStatDir for Windows looks a lot like Grand Perspective 0.99 for Mac OS X, I figured I might as well post a link to it here. The graphical interpretation sure looks similar to me too. But, it is a common way of visualizing multiple volumes of something. I like the way WinStatDir presents the detailed information in a list that refocuses as you point to a different part of the graph. If WinStatDir got its inspiration from Grand Perspective, I hope the author of Grand Perspective returns the favor and adds the detailed information list :-)