WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
ncdu - A disk usage analyzer with an ncurses interface, aimed to be run on a remote server where you...
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 Disk Usage Analyzer - Baobab Disk Usage Analyzer is one of the light-weight disk analyzers that offers you a chance to view and monitor the disk usage & folder structure without any hassle.
TreeSize - TreeSize tells you where precious disk space has gone to.
Gdu - Gdu is one of the smart open-source disk analyzers specially designed for Linux that provides you complete information related to the disk space.