WinDirStat
Open Source
WinDirStat is a disk usage statistics viewer and cleanup tool for Windows based systems.
Baobab
Open Source
Baobab is a disk usage analyzer is a graphical disk usage analyzer for GNOME.
GrandPerspective
Open Source
GrandPerspective is open source software for Mac OS X used for disk space analysis.
SpaceMonger
Commercial
SpaceMonger is a tool for keeping track of the free space on your computer.
MindGems Folder Size
Free
Folder Size is a freeware disk size analysis tool that will display the directory sizes and folder tree sizes.
FolderSizes
Commercial
FolderSizes is a disk space management tool.
TreeSize
Freemium
TreeSize Free is a free disk space manager for Windows. The software shows you the sizes of folders including all subfolders.
DaisyDisk
Commercial
DaisyDisk is a disk space analyzer for OS X.
ncdu
Open Source
ncdu (NCurses Disk Usage) is a disk utility for Unix systems.
WizTree
Free
WizTree gives you more control over how you see your files, in addition to letting you learn more about them from one look.
SequoiaView
Free
SequoiaView is a disk browsing tool based on the principle of treemaps.
Compare GD Map with alternatives
Compare GrandPerspective and GD Map and decide which is most suitable for you.
Compare MindGems Folder Size and GD Map and decide which is most suitable for you.