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FolderSizes provides an engaging, interactive disk space analysis experience that you must try yourself to truly appreciate. More than just a series of diverse reports, FolderSizes allows you to visualize your disk space usage from multiple perspectives, like SequoiaView.

HDGraph helps you to free disk space : it finds for you the largest folders on your drive.

KDirStat was a graphical disk usage utility based on KDE 3 libraries, The information provided is similar to the Unix "du" command. In addition to that, it comes with some cleanup facilities to reclaim disk space.

RAWGraphs is an open source app built with the goal of making the visualization of complex data easy for everyone. Born as tool for designers and vis geeks, RAWGraphs aims at providing a missing link between spreadsheets and vector graphics editors.