phpWebFTP offers a way of connecting to you FTP server, even when you
are behind a firewall or proxy not allowing traffic to FTP servers.
This is very common in business networks. phpWebFTP overcomes this
issue by making a FTP connection from your webserver to your FTP server
and transfering the files from this web server to your webclient over
the standard http protocol. phpWebFTP is free software and the source
is available under GNU license.

WWW: http://www.phpwebftp.com/