And the other rich source for information are our forums. Do not hesitate to ask questions and post bug reports there, we will be glad to answer them.
Currently we don't have Telerik Trainer (http://www.telerik.com/support/teleriktrainer.aspx) for RadControls for Silverlight and WPF, but we are working hard on providing the same quality interactive videos as RadControls for ASP.NET.
Greetings,
Valeri Hristov
the Telerik team
Check out Telerik Trainer, the state of the art learning tool for Telerik products.