GoodSync - GoodSync provides highly reliable file backup and synchronization for both individuals and businesses.
Synchromat - Synchromat is file and folder synchronization software for Windows.
rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.
MirrorFolder - MirrorFolder is a real-time folder synchronization and backup software
Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
CopyQueue - CopyQueue - Copying under control.