Introducing the Microsoft Web Farm Framework

The Microsoft Web Farm Framework is a free product that enables you to easily provision and mange a farm of web servers.  It enables you to automate the installation and configuration of platform components across the server farm, and enables you to automatically synchronize and deploy ASP.NET applications across them.  It also supports integration with load balancers – and enables you to automate updates across your servers so that your site/application is never down or unavailable to customers (it can automatically pull servers one-at-a-time out of the load balancer rotation, update them, and then inject them back into rotation).

http://weblogs.asp.net/scottgu/archive/2010/09/08/introducing-the-microsoft-web-farm-framework.aspx