Silverlight 3 introduced an out of browser mode that provided a standalone experience for running Silverlight applications using the same execution sandbox model as when running in the browser. For the upcoming Silverlight 4, the out of browser support is being extended to allow an application to either run in a sandbox or as a trusted program. A variety of new resources are available covering these extensions.
Joe Stegman has a Channel 9 video covering Silverlight 4 out of browser mode improvements. As Joe mentions during the interview, he also gave a PDC talk on the subject. Out of browser execution was also a part of the overview that Karen Corby gave for Silverlight 4 at PDC. Finally, the Silverlight team has prepared a security whitepaper for Silverlight 4, including these new extensions.
Explore enhancements to the app experience, the ability to host HTML content within Silverlight, and playback rights-protected media when offline. Get details on the new extensions to the sandbox that allow apps to run with elevated privileges and access the file system or interop with desktop components via Automation.
Microsoft Silverlight 4 Overview by Karen Corby
Take a tour of the new features in Silverlight 4 including a dive into some of the new ready for business features like printing, rich text support, and expanded databinding support. Also hear about exciting Silverlight additions to the media stack, and get an introduction to the Silverlight 4 elevated trust out of browser model.