Dropbox - Online Sync and File Sharing
Filestash - Filestash is a modern client for FTP, SFTP, S3, WebDAV, Minio,...
Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
Syncany - Syncany is an open-source cloud storage and filesharing application.
Google Drive - Access and sync your files anywhere
FTPSync.pl - FTPSync.pl is a PERL skript to synchronize a local directory tree and a remote FTP directory tree.