Tunneling through a hostile proxy?

This may have been discussed before, but a Google search has turned up lacking. Given internet access from a private intranet, through an HTTP proxy out of the user's control, is it possible to establish a secure tunnel to an outside server? I'd expect that ordinary SSL connections will secure user <-> proxy and proxy <-> server separately, with the proxy able to observe cleartext. Could an SSH connection be made under these conditions? Pointers appreciated, thanks. -- Roy M. Silvernail Proprietor, scytale.com roy@scytale.com