Silverlight for SharePoint 2010 is one of the newly added features to SharePoint 2010. It includes a rich set of APIs that allow you to interact with SharePoint data – lists, document libraries, sites etc., from your Silverlight application.
I am in the middle of reviewing the Microsoft Silverlight 4 and SharePoint 2010 Integration book by Gaston C.Hillar and here is the first chapter of the book (which you can download) :
The first chapter introduces you to Silverlight 4, building very simple Silverlight 4 application and then hosting that Silverlight application into SharePoint 2010. The chapter does not yet cover the SharePoint 2010 Silverlight Client Object Model.
You can however purchase the full e-book or order a copy here (I think ePub format is also available for the iPad lovers )