Sequoia view is a free program for visualising hard disk usage by squares. It employs an innovative algorithm for visualising all files at once as squares of different size, according to the size of the file. This way it is easy to spot files that take up the most disk space, even if they're hidden deep in the directory tree. Typical hard drives of the mid-1990s. ...
An alternate tool to visualize hard disk usage are windirstat, or FolderSize to list the files.
Linux Square Disk Usage Visualization
For Linux we have duv, the Visual Disk Usage tool, somehow a visual extension of the Unixdu command. Try duv --help first to know the commands. It has been suggested that this article or section be merged with Linux distributions. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ...
The tool Baobab lists the files and also visualizes hard disk usage, as Sequoia does by squares.
Circular Disk Usage Visualilization
A different circular representation is given by Filelight. The equivalent tools for Windows are Overdisk and Scanner.