Ssh execute remote commands

Ssh is a very very useful tool and some tricks with it will help you a lot of time and typing. For example I want to transfer a file remote like my ssh-key file. I have a few options:

• use scp to transfer the file, then login into the remote system and execute the commands.
  
• use a different mechanism to transfer the files(ftp etc), login and execute the commands.
  
• do it all in one command ... this is the cool one - see bellow
  

shell$ cat ~sd/.ssh/id_rsa.pub | ssh root@192.168.0.105 'cat - > .ssh/authorized_keys'
shell$ cat ~sd/.ssh/id_rsa.pub | ssh root@192.168.0.105 'cat - > .ssh/authorized_keys2'

# usually the authorized_keys is a link to authorized_keys2 but in this I just have two separate files.
# as you can see is nothing else to do :)