Puppet. If you’re a systems administrator you need to learn it, love it and live it. We used Puppet at Terremark for Linux systems but never really seemed to leverages more than 20% of its capability. Since then Puppet 3 has been released and I’ve just finished taking an Intro class at work. Man, this stuff is cool. Between VM templates in ESXi and Puppet I’ll be able to overload my ESX hosts in no time flat and do it in a completely automated fashion. Whee!!!
Of course automation is a huge time saver. It can (and often does) completely scramble your environment in record time. As with any automated tool the development cycle *MUST* include thorough testing. Fortunately Puppet has a lot of features that let you do exactly that.