Silverlight is maturing rapidly as a platform for building compelling Rich Internet applications and delivering high definition content. A maintainable Silverlight 3 application requires the same care and design as any other enterprise application and the available tools and patterns are changing quickly. In this talk, we’ll build up a sample application using Presentation Layer patterns, loosely coupled smart client software techniques with Prism and Unity, service consumption with RIA services, and making your applications compose able with the Managed Extensibility Framework.