MobaSSH is a free SSH server for Windows (XP,Vista,7,2008), compatible with any ssh client (OpenSSH client, Putty, ...). MobaSSH comes with an easy to use installer and some useful GNU utilities...
Free, simple but robust and reliable SSH(2) and SFTP Server for Windows. It features 3 authentication types (including public-key auth) as well as a good SFTP subsystem and channel forwarding.