Tunneling through a hostile proxy?

[Roy M. Silvernail]

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 at scytale.com