WinSCP open source SFTP and FTP client for Microsoft Windows
Furthermore WinSCP can act as a remote editor: when you click on a file, for example a text document in the remote file manager, it transfers the file to the local machine and opens it in the integrated editor. Whenever the document is saved, the remote version is updated automatically.
Development of WinSCP started around May 2000 and was originally hosted by the University of Economics in Prague. Since July 16, 2003 it is licensed under GPL. It is popular among the iPhone Jailbreak community as a way of transferring data to and from the device and even comes with a portable edition, useful if you want to have it on your USB device or dropbox.
WinSCP 4.2.6 is available for download here, the complete changelog can be found there.