cat ~/.ssh/id_rsa.pub | ssh userid@hostname.com 'mkdir -p .ssh && touch .ssh/authorized_keys && cat - >> .ssh/authorized_keys'
Just replace the userid and hostname.com as needed.
Where my life gets parked.
cat ~/.ssh/id_rsa.pub | ssh userid@hostname.com 'mkdir -p .ssh && touch .ssh/authorized_keys && cat - >> .ssh/authorized_keys'