ssh-add script.

Here's little script that check to see if the ssh-agent knows any keys. If not, it asks for your passphrase. Then it executes ssh.

#!/bin/sh
#DTPD#
## $HOME/bin/ssh ##
if ! (ssh-add -l > /dev/null); then
  ssh-add;
fi
echo ssh "$@";
exec /usr/bin/ssh "$@";

Of course you have to have the ssh-agent working correctly in the first place.