Changing the Mac OS X ssh Port
As I wrote in a comment for the macgeekery.com article "Basic Mac OS X Security":
One simpler way to change the ssh port is to edit /System/Library/LaunchDaemons/ssh.plist. That file contains these lines:
<key>SockServiceName</key>
<string>ssh</string>
Which is what refers to the "ssh" line in /etc/services. You can change that to any other name from /etc/services, or you can change it to a number, like 2200. As far as I can tell, this also takes care of opening the correct port(s) on the firewall.
I learned this while I was reading the manpage for launchd.plist. I was actually trying to find out where launchd.plist is located on the system, so I was looking the directories mentioned in that document.
I also learned from a comment on macosxhints.com that it's not difficult to open more than one port for the same service:
http://www.macosxhints.com/comment.php?mode=view&cid=96607
Which is how I tested my new ssh port without disabling the existing one.