A set of enhanced Windows Server application server capabilities code-named “Dublin,” which offer greater scalability and easier manageability, and will extend Internet Information Services (IIS) to provide a standard host for applications that use workflow or communications.

After these enhancements to the Windows Server application server will simplify the deployment, configuration, management and scalability of composite applications, while allowing developers to use their existing skills with Visual Studio, the .NET Framework and IIS.

Some Features are

Provide standard host for WF and WCF applications

First CTP will be provided on PDC. The community feedback will influence the RTM.
Application Server “Dublin” will first become available after the release of the .NET Framework 4.0 and Visual Studio “10”.
Application Server “Dublin” will initially be made available for download and use by Windows Server customers; later, “Dublin” will be included in future releases of Windows Server.
Application Server “Dublin” will extend Internet Information Services (IIS) to provide a standard host for applications that use workflow or communications.
It will provide support for Oslo modeling platform.
It will support existing .NET apps.
It will support integration with BizTalk Server (in this context called "Integration Server").

Pre-built developer services

Message-based correlation
Message forwarding service
Content-based message routing
Compensation service for long-running transactions

Greater scalability and easier manageability

Enable scale-out of stateful workflow applications
Persisting and rehydrating state for high scalability
Enhanced management and monitoring functions
Tracking store for workflow events

Supports “Oslo” modeling platform