Syncany - Syncany is an open-source cloud storage and filesharing application.
FileZilla - FileZilla is an FTP, or file transfer protocol, client. It lets individuals transfer single files or batches to a web server. For many years, FTP was the standard for website design. Read more about FileZilla.
Filestash - Filestash is a modern client for FTP, SFTP, S3, WebDAV, Minio,...
PTFTP - Simplistic and intuitive explorer-like ftp client. Open source.
Dropbox - Online Sync and File Sharing
WinSCP - WinSCP is an open source free SFTP client and FTP client for Windows.