Microsoft have released a preview version of the latest release of their Web Farm Framework.
The Web Farm Framework is a system which allows you to quickly and easily scale your website within your datacenter. It's aimed at companies who have a medium size deployment of servers already, and who need a way to quickly and efficiently add more servers to their cluster to manage their growth. It manages updates, allows for highly customised provisioning, and allows additional components to be added to the platform.
The Web Farm Framework makes use of the Web Platform Installer for platform provisioning, integrates with Application Request Routing as well as other load balancing products. It provides snapshots of server readiness, and up-to-date information on the status of existing servers and the entire pool.
Some added bonuses that I think are pretty cool - it has a set of APIs for programmatically managing your configuration, and can be configured through cmdlets for Windows PowerShell.
More information on Microsoft Web Farm Framework on the IIS.net website.