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.
PTFTP - Simplistic and intuitive explorer-like ftp client. Open source.
WinSCP - WinSCP is an open source free SFTP client and FTP client for Windows.
Cyberduck - A libre FTP, SFTP, WebDAV, S3, Backblaze B2, Azure & OpenStack Swift browser.
lftp - lftp is a command-line file transfer program which besides FTP, also supports FTPS, HTTP, HTTPS...
Transmit - Transmit is an FTP client for Mac OS X and Mac OS Classic (which is unsupported).