I just "found" kdirstat for KDE. It is a very nice program, that does have a Windows clone called WinDirStat. To install this program using Kubuntu, just use

$ sudo apt-get install kdirstat

and use the CLI to invoke it using kdirstat. There is no menu item..at least one didn't show up for me.

kdirstat overview

After a short amount of scanning time, you are presented with a visual representation of your organized file system starting at whichever folder you selected when the program started. From here, you can compress and delete files, and very easily see where the hogs are.

kdirstat drill down

This is an invaluable tool for system administrators and I have just begun to explore the features of this free tool.