WinSCP is an open source SFTP client and FTP client for Windows. Its main function is the secure file transfer between a local and a remote computer. Beyond this, WinSCP offers basic file manager functionality.
Cyberduck is an open source FTP, SFTP, WebDAV, Cloud Files and Amazon S3 browser for the Mac. It features an easy to use interface with quickly accessible bookmarks. The outline view of the browser allows to browse large folder structures efficiently and you can quickly preview files with Quick Look. 
FireFTP is a free, secure, cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers.
Core FTP LE – free Windows software that includes the client FTP features you need. Features like SFTP (SSH), SSL, TLS, IDN, browser integration, site to site transfers, FTP transfer resume, drag and drop support and much more.
FileZilla, the free FTP solution. Both a client and a server are available. FileZilla is open source software distributed free of charge under the terms of the GNU General Public License.