SSH login without password

http://linuxproblem.org/art_9.html
http://askubuntu.com/questions/46930/how-can-i-set-up-password-less-ssh-login
http://askubuntu.com/questions/54670/passwordless-ssh-not-working

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'

or 

using ssh-copy-id

[Note]
If not working, try chmod 600 ~/.ssh/authorized_keys
[Note]
$HOME 0755
$HOME/.ssh 0700
$HOME/.ssh/* 0600