Baobab is a disk usage analyzer is a graphical disk usage analyzer for GNOME.

DiskUsage provides a way to find files and directories on storage card which consumes a lot of space.

Folder Size is a freeware disk size analysis tool that will display the directory sizes and folder tree sizes.

GrandPerspective is open source software for Mac OS X used for disk space analysis.

Scanner is a tool uses a sunburst chart to display the usage of your hard disk or other media.

SpaceMonger is a tool for keeping track of the free space on your computer.

DaisyDisk is a disk space analyzer for OS X.

Filelight is a KDE graphical disk usage analyzer, part of the KDE Utils package.

GdMap is a tool which allows visualizing disk space.

JDiskReport enables you to understand how much space the files and directories consume on your disk drives, and it helps you find obsolete files and folders.

SequoiaView is a disk browsing tool based on the principle of treemaps.

SpaceSniffer is a freeWare and portable tool application that lets you understand how folders and files are structured on disks.