MacOSXHints.com has a sweet little tip to get tab completion for ssh. Just enter the following line at the bottom of your .bash_profile script for tab completing goodness.

complete -W "$(echo `cat ~/.ssh/known_hosts | cut -f 1 -d ' ' | sed -e s/,.*//g | uniq | grep -v "\["`;)" ssh

Perhaps the best part is that you can type ssh-[tab]-[tab] to quickly see all of the hosts that are in your known hosts file and then quickly pick out that IP or host name that you can never remember.