I came across a nice blog on Silverlight and WCF RIA Services by Mike Taulty from Microsoft UK. Thought of sharing it with you.
Just read through it in free times.
Silverlight and WCF RIA Services (1 – Overview)
Silverlight and WCF RIA Services (2 – Services)
Silverlight and WCF RIA Services (3 – Client)
Silverlight and WCF RIA Services (5-Authentication)
Happy Coding!!!