GrandPerspective is a free and open source application for Mac OS X that helps visualize disk usage and find large files. It scans a chosen folder, such as your home folder, and creates a graphic representation of the disk usage in that folder. The size of each file is represented by a rectangular box, with the larger files taking up more space. GrandPerspective can be used to quickly identify large files and folders that are taking up a lot of disk space, so that they can be removed or moved to a different location. It can also be used to help identify duplicate files and folders, so that they can be removed to free up space. The app also includes a built-in file viewer so users can quickly preview the contents of any file without having to open it.
Discontinued The program seems to be no longer updated. The latest version, 2.13, released in July 2012, is fully functional and can still be downloaded from the official website.
Discontinued The official website is no longer available. The latest version, 1.3, released in June 2006, can still be downloaded from Softpedia.
Discontinued The program appears to be dead, as announced in a tweet from the author: https://twitter.com/bartheph/status/742596462807265280. The website and changelog appear to be abandoned. The latest version, 0.4.3, released at the end of 2015, can still be downloaded from the official website.
Gives a good overview, with an easily selectable level of detail.