Free FTP Clients
curl is a command line tool for transferring data with URL syntax, supporting DICT, FILE, FTP, FTPS, Gopher, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS, Telnet and TFTP. curl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM, Negotiate, kerberos...), file transfer resume, proxy tunneling and a busload of other useful tricks.
Fugu - A Mac OS X SFTP, SCP and SSH Frontend. Fugu is a graphical frontend to the commandline Secure File Transfer application (SFTP).
Core FTP Lite
A free FTP Client with SSL/TLS, SSH/SFTP, site to site transfers, dragdrop, browser integration, user-friendly interface(s), FTP/HTTP Proxy, Socks 4/5 support, remote file searching, queue manager, auto retry and resume of transfers, transfer bandwidth control, htaccess editing, advanced dir listings, queueing of multiple FTP transfers on multiple sites, sessions, start, stop, and resume of FTP transfers, advanced directory listings, .htaccess editing, auto s/key support, keep alive, auto-reconnect, file permissions (chmod), and much more.
FileZilla is a fast FTP client for Windows with a lot of features. FileZilla Server is a reliable FTP server. (open source gpl license)
SmartFTP is FREE for personal and educational use.
Portable FileZilla allows you to carry a whole FTP client with you on an iPod, USB thumbdrive, portable hard drive or any other portable media.
AceFTP 3 Freeware
Version 3.00.4 - 2.3 Mb, Win XP, Me, 2000, NT, 98, 95
FTP Commander 8.02
FTP Commander is a simple and easy to use FTP client for windows.
i.Ftp is a little graphical FTP client originally developed for Beos, but now available for windows - source code is also available.