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.
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?
Telerik Public Issue Tracking
system and vote to affect the priority of the items