SSH Login to my Ubuntu 8.04 machine was slow. (It would delay about 5 seconds after I issued the ssh command for the remote machine to request a password.) I believe this is because the remote machine is on my home network, and I have set up it’s hostname using host entries instead of having a true DNS name.
I edited the /etc/init.d/sshd_config file and added the single line:
UseDNS no
which fixed this problem as soon as I restarted the SSH server, with
sudo /etc/init.d/ssh restart