SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.

Baobab - Distributor of workload automation, financial statement reporting, data access, IT Asset Management and Service Desk software solutions.

WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.

Disk Inventory X - Disk Inventory X is an open source disk space analyzer and disk management tool for the Mac OS X operating systems that allow the OS X users to check for the availability of free space in their machines.

SpaceMonger - SpaceMonger helps you understand what's occupying your hard drive and more effectively clean it up without worrying about losing anything important in the process.

JDiskReport - JDiskReport enables you to understand how much space the files and directories consume on your disk...