I've also been hearing a lot about Windows Server App Fabric. Here is a quick blurb from the App Fabric white paper.
AppFabric Hosting Services (originally code-named “Dublin”) doesn’t create some entirely new hosting infrastructure. Instead, it builds on what’s already provided by Internet Information Services (IIS) and Windows Process Activation Service (WAS). On this foundation, AppFabric Hosting Services adds extra capabilities for running and managing WCF services, including workflow services. Figure 7 illustrates this idea.
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