SSH Using Public Key Useful Sites

password-less ssh
http://www.cyberciti.biz/tips/ssh-public-key-based-authentication-how-to.html 

multiple ssh keys 
http://www.cyberciti.biz/tips/linux-multiple-ssh-key-based-authentication.html

SSH using public Key
http://youritguy.wordpress.com/2010/10/12/centos-5-5-ssh-with-public-key-authentication/