Or, "How to login over SSH without a password".

First of all, you'll need to have generated an SSH public DSA key using the following commands:

cd ~ && ssh-keygen -t dsa

Then, you can add the following bash function to your .bashrc (or similar) and just type 'scpdsa user@hostname' to add your public key to your 'authorized_keys' file on the server.

function scpdsa {
  if [[ -z "$1" ]]; then
    echo "!! You need to enter a hostname in order to send your public key !!" 
  else
    echo "* Copying SSH public key to server..." 
    ssh ${1} "mkdir -p ~/.ssh && cat - >> ~/.ssh/authorized_keys" < ~/.ssh/id_dsa.pub
    echo "* All done!"
  fi
}

-- updated to use simpler and quicker method.