As part of the release of vSphere 5, VMware also released version 4.2 of its runbook automation software, called vCenter Orchestrator. This version is the follow up of version 4.1 which was released in August 2010. This version provides mainly bug fixing, mainly because VMware focussed more on releasing more plugins for Orchestrator, which are 7 at this moment.
When you install vCenter Server 5.0 this version will already be installed, if you want to install Orchestrator on another system, you can use the standalone installer.