I just tested WinSCP for you, it works with nothing but an open SSH port on the server--was very straight-forward.
It doesn't allow a true mount from looks of things, it gives you one of those left/right copy things instead.
I bet there is an SSHFS client for windows out there somewhere though if you really need that.
Edit:There is an old program from Novel that will do this, it's apparently free, but I haven't tested it. You might give it a try: http://www.novell.com/coolsolutions/qna/999.html