cPanel - With its first-class support and rich feature set, cPanel & WHM has been the web hosting industry's most reliable, intuitive control panel since 1997.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
ServerPilot.io - Centralized hosting control panel for Wordpress and PHP web sites
TreeSize - TreeSize tells you where precious disk space has gone to.
Webmin - Webmin is a web-based interface for system administration for Unix.
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.