My congratulations to everyone at Microsoft involved in Vista and .NET 3.0 development for getting Release Candidate 1 out. The celebrations at Redmond seem to have been captured best by Pablo Fernicola's blog entry with photographs.
Although the RC1 of .NET 3.0 is available here and the SDK is available here, it appears that the Visual Studio extensions won't be ready for another week or so.
Which means that if you're using my book Applications = Code + Markup: A Guide to the Microsoft Windows Presentation Foundation to learn how to code killer WPF apps, you'll probably still want to use the June CTP, as described on the Applications = Code + Markup page of my Web site. Without the VS extensions, you won't be able to load any of the .CSPROJ files from the downloadable source code from the book into Visual Studio, or use Visual Studio to create new WPF projects.
HOWEVER, if you just can't wait to install RC1 and you also want to start learning WPF programming with my book, you can build WPF projects on the command line using the MSBuild utility provided with the SDK.