We have a product called IntegralFTP, which allows you to do the sort of thing Peter's referring to (unless I've misunderstood it - sorry). You can use it to do FTP, SFTP and FTPS operations from Javascript. It's basically a Javascript class that uses an invisible Java applet to do the actual FTP/FTPS/SFTP comms. We think it's pretty cool. :-)
You can find it at http://www.enterprisedt.com/products/integralftp/overview.html.
You can find it at http://www.enterprisedt.com/products/integralftp/overview.html.