Hi Dan.
Perhaps you are looking for some utility like this:
http://sshmenu.sourceforge.net/
sshmenu also works with ssh-agent.
I have it installed, but I prefer to use bash-completion:
http://fedoratutorials.com/2007/10/24/pow-bash-completion-bash-auto-compl...
So if I type:
ssh ar<tab><tab>
It shows me all hostnames from my known_hosts file beginning with "ar"
Ashay