Silverlight 2 could be an interesting platform for business applications. It comes with a set of VB like controls, yet it could be deployed like a web application. The silverlight 2 runtime is only 3.5 MB, yet it supports C#/VB language and client-side library with good set of functionalities, includding LINQ and web service communication library.

A Silverlight 2 business application would typically communicate with back-end via web service calls. Interestingly, .NET 3.5 sp1 also comes with ADO.NET data service that allows us quickly turn database into a web service. The following are the resources, from the front-end to the back end, that allows us to construct application using architecture:

Silverlight 2 control demo Download

Using ASP.NET authentication in Web Service with Silverlight

Accessing ASP.NET membership, role and profile from Silverlight

ADO.NET Entity Framework and ADO.NET Data Service Framework

The following are additional resources that allows us to create rich applications:

Silverlight Rich TextBox

Silverlight and Virtual Earth and Album Atlas (Created with VIEWS)

Silverlight File Browser and Upload and Silverlgiht File Uploader

Unit Testing: Silverlight unit testing, Silverlight NUnit

Dependency injection or IOC: SLUnity, Bloom, ninject

Model view presenter framework: MVC#

AOP for Silverlight: PostSharp

Lastly, there is an MSDN casts on this subject by Shawn Wildermuth. I would also recommend Shawn's blog.