We have many years experience with file transfer, and are often asked by our customers for recommendations on free FTP, FTPS or SFTP clients. For their convenience, we are now hosting the installers for these clients on our site.
The main criteria for inclusion is that these are 1) clients with solid reputations; 2) the clients are in widespread use; and 3) these are clients we regularly use ourselves. They are free for commercial use, and distributed under the GPL license.
The clients below have been tested extensively with our secure file transfer server for Windows, CompleteFTP.