WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
Bashupload - Upload files from command line to share between servers
TreeSize - TreeSize tells you where precious disk space has gone to.
FilePizza - Open source application used to transfer file via WebRTC and WebTorrent.
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.
BlackHole File Transfer - Blockchain-based file transfer. Designed for everyday use.