Syncany - Syncany is an open-source cloud storage and filesharing application.
Dropbox - Online Sync and File Sharing
FTPSync.pl - FTPSync.pl is a PERL skript to synchronize a local directory tree and a remote FTP directory tree.
ownCloud - ownCloud is an open source project enabling businesses to host their own cloud storage while maintaining regulatory and compliance needs.
Google Drive - Access and sync your files anywhere
Mega - Secure File Storage and collaboration