Silverlight 2 Release Candidate is now available to developers for testing purposes and to help prepare your Silverlight 2 Beta 2 applications for the release of Silverlight 2. This release is therefore not intended for public deployment, as end users will not have a way to install a suitable plug-in to view the application. No existing public versions (released or beta) of Silverlight 1.0 or 2 Beta 2 will be auto-upgrade to this runtime. As said this is only for developers.
As mentioned on this detailed post of Scott Guthrie, you can download today’s Silverlight Release Candidate with VS and Blend support for it here.