Automagically install SSH public keys into authorized_keys on a remote machine

There is a handy little utility called 'ssh-copy-id' that simplifies getting your ssh public key into a remote machine's authorized_keys. The syntax is:

ssh-copy-id [-i [identity_file]] [user@]machine

It handles creating the ssh directory and authorized_keys file on the remote side (if necessary), and setting the right file permissions. Neat!