To help people come up to speed with Silverlight 2, I've written a simple Silverlight application and put together a series of step by step tutorials that explain the different programming concepts behind it (controls, layout management, networking, data-binding, styles, user controls, templates, etc). I also added a tutorial post that demonstrates how to migrate the application outside of the browser and enable it to run as a desktop application using WPF and the full .NET Framework.
Below are the pointers to the 8 tutorials I've put together:
The application I've built the tutorials around is a simple search front end to the popular Digg.com site, and allows users to type in search topics and browse Digg stories that match them.
<Download Code> Click here to download a completed version of the Digg client sample. </Download Code>
All of the UI in the application is built using Silverlight's built-in WPF UI framework. The application uses the Silverlight networking stack and cross-domain access support to query the Digg REST API directly, and uses LINQ and LINQ to XML to query/transform the returned data into DiggStory objects that I databind the UI against:

The application supports a master/details data interaction model that allows users to select stories from the search list and quickly drill into more details about them. A user can jump to the Digg article directly from the details form, or close it and pick another story to drill into:

The entire application is implemented in about 35 lines of C# code and 75 lines of XAML page/user-control markup. It only uses controls and libraries built-into Silverlight.
<Download Code> Click here to download a completed version of the Digg client sample. </Download Code>
If you have used WPF before the UI concepts I discuss in the tutorial series will all be very familiar. If you haven't used WPF before, the tutorials should provide a good overview of the fundamental programming concepts in it, and hopefully provide you with the basic knowledge necessary to start building either Silverlight 2 or WPF applications.
Hope this helps,
Scott