You can find information and links for download of the runtime and SDK at the MSDN beta site.
We have added a lot of content for this release, and are working on more for RTM. We'll continue to monitor this blog and other feedback sources for your suggestions on how to improve the content or discoverability.
The online documentation has not yet been updated for RC, but that will be remedied soon.
We are the Windows Presentation Foundation SDK writers and editors.