SSH with no local home directory?

[lug at the-leveys.us (Don Levey)]

Here's my situation:
I need to find a way, if possible, for a user with no local home directory
to make an ssh connection to another host.  The problem here is that
normally the remote machine's RSA key is stored in ~/.ssh/known_hosts, but
with no home dir that won't work.  Is there any system-wide known_hosts file
I could implement that would be checked first (or instead)?  The thing I'm
trying to do is to get the machine to connect to another based upon a web
page connection, but the user ID running the web server has no home dir or
login.
 -Don