At the start of December (2010) we released the Native Extensions for Silverlight (NESL), version 1.0.
NESL allows developers to build incremental user experiences that can be run cross platform but will light up with additional features when run on Windows 7.
You can download from: http://code.msdn.microsoft.com/nesl
While Silverlight 4 supports accessing COM automation components from elevated trust OOB applications, many Windows platform features are currently not available through COM automation. This makes them inaccessible to such Silverlight OOB apps. Native Extensions for Microsoft Silverlight(NESL) is an effort to incrementally build a library of components that expose select Windows 7 features through COM automation, making them easily available to Silverlight 4 OOB applications running with elevated trust.
The current version of NESL provides access to Windows 7 features like Sensors, Portable Devices, Speech, Taskbar and more. NESL is made up of a set of COM automation based runtime libraries, Silverlight wrapper libraries usable from Silverlight 4 OOB applications, sample applications with source, API documentation, and a developer's guide.