Puppet
Some useful links to explain the concepts of Puppet
Concepts
Official Documentation
Others
http://www.slashroot.in/puppet-tutorial-introduction-puppet-configuration-management-tool
http://www.slashroot.in/puppet-tutorial-how-does-puppet-work
http://www.slashroot.in/puppet-hiera-tutorial-example-configuration
https://www.youtube.com/watch?v=73xeSTz8AeA&list=PLtNErhYMkHnEu1_ZHSJt1xF–zU35dRgZ
http://codingbee.net/tutorials/puppet/puppet-what-is-puppet/
http://opensourceforu.efytimes.com/2009/06/puppet-show-automating-unix-administration/
http://www.linuxuser.co.uk/tutorials/puppet-server-management
https://www.linux.com/learn/tutorials/325201-introduction-to-puppet-streamlined-system-configuration
http://www.linuxjournal.com/magazine/automate-system-administration-tasks-puppet