Dropbox - Online Sync and File Sharing
rsync - rsync is a software application for Unix which synchronizes files and directories from one location...
SugarSync - SugarSync is a cloud file sharing, file sync and online backup service that is simple, powerful and easy to use. Get a 30 day free trial!
FreeFileSync - Download the latest FreeFileSync 10.4. FreeFileSync is a free open source data backup software that helps you synchronize files and folders on Windows, Linux and macOS.
Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.
Duplicati - Free backup software to store backups online with strong encryption. Works with FTP, SSH, WebDAV, OneDrive, Amazon S3, Google Drive and many others.