Filelight is an alternative file manager for KDE.  Filelight creates an 
interactive map of concentric segmented-rings that helps you to visualize 
disk usage on your computer.

It is like a pie-chart, but the segments are nested, which allows you to 
see not only which directories take up all your space, but which files and
subdirectories are the real culprits.

You can also browse remote servers using the fish:// or ftp:// KIO slave 
inside Filelight.