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.

GdMap is a tool which allows visualizing disk space.

ncdu (NCurses Disk Usage) is a disk utility for Unix systems.

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

DaisyDisk is a disk space analyzer for OS X.

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

FolderSizes is a disk space management tool.

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.

RidNacs is a free and very fast disk space usage analyzer for Windows.

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