The Web Platform Installer Beta (Web PI) provides a single, free package for installing and configuring Microsoft's entire Web Platform, including IIS7, Visual Web Developer 2008 Express Edition, SQL Server 2008 Express Edition and the .NET Framework. Using the Web Platform Installer’s simple user interface, you can select specific components or install the entire Microsoft Web Platform onto your computer. To help you stay up-to-date with product releases, the Web Platform Installer always contains the most current versions and new additions to the Microsoft Web Platform.
On the open source side, the Web Application Installer Beta is designed to help get you up and running with the most widely used Web Applications freely available for your Windows Server. Web AI provides support for popular ASP.Net and PHP Web applications including Graffiti, DotNetNuke, WordPress, Drupal, OSCommerce and more. With just a few simple clicks, Web AI will check your machine for the necessary pre-requisites, download these applications from their source location in the community, walk you through basic configuration items and then install them on your computer.
CNET's thoughts on Microsoft assisting in 3rd-party open source distribution
Finally, everyone should look at the Microsoft Web Platform blog, particularly the Inspiration section