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...
DaisyDisk - DaisyDisk is a disk analyzer tool for OS X that visualizes hard disk usage and allows to free up hard disk space.
WizTree - WizTree quickly finds the files and folders using the most space on your hard drive. It scans the MFT (Master File Table) instead of crawling the entire disk which makes it very fast.
Filelight - Filelight is an application to visualize the disk usage on your computer.
TreeSize - TreeSize tells you where precious disk space has gone to.