As I always forget the exact syntax and am too chicken-hearted to fool around, I note down the command to add one's public key to the authorized keys on the remote machine (to login using pub/private key pair only) here. Use the following command (id_rsa.pub might be id_dsa.pub on your site).

cat ~/.ssh/id_rsa.pub | ssh user@site.com "cat - >> ~/.ssh/authorized_keys"

That's it,
iss