Vdirsyncer is a command-line tool for synchronizing calendars and addressbooks between a variety of servers and the local filesystem. The most popular usecase is to synchronize a server with a local folder and use a set of other programs to change the local events and contacts. Vdirsyncer can then synchronize those changes back to the server.

Trilium Notes is a hierarchical note taking application with focus on building large personal knowledge bases.

DSynchronize is a stand-alone utility that let you periodically synchronize two or more folders on Hard Disk, Floppy Disk, LAN, USB Key, CD-DVD and FTP server.

Backup and synchronize tool for Windows 10 (32 & 64 bit), Win8, Win7, Vista, Win XP, Win 2000, Linux (Wine).

Python (+ rsync or rclone) based intelligent file sync with automatic backups and file move/delete tracking.