With Q2 2010 SP1 we shipped only binaries for Silverlight 3. You can find them under Your Account->Free Trials->RadControls for Silverlight->Silverlight 3 - DLLs only. You can also follow this link.
Greetings,
Hristo
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Explore the
Telerik Public Issue Tracking
system and vote to affect the priority of the items