This utility runs "du" to scan directories of your choosing, then displays a
graph which emphasizes the subdirectories where the largest files are kept, and
optionally lists the files themselves.  You can descend into the directory
tree, or back out, by clicking on the graph.  If you save the output of "du" in
a file, xdiskusage can analyze that too.  PostScript output is available.

WWW: http://xdiskusage.sourceforge.net/