Today's $10 Deal of the Day from APress at
http://www.apress.com/9781430229919 is Introducing Silverlight 4
"Brings you up to speed with version 4 of Silverlight quickly and
efficiently. The book builds off your understanding of the basics of
.NET coding and WPF, allowing your journey to Silverlight 4 proficiency
to be as quick and painless as possible."