NETFX 3.0 just went live on the web today, you can download it here. NETFX 3.0 contains Windows Presentation Foundation (WPF), Windows Communication Foundation (WCF), Windows Workflow, and Windows Cardspace.
You can find out more information about the Go Live program here.
Finally, you can also download the SDK for this release here.
Congrats to the team for reaching this important milestone! I'm looking forward to the feedback on release. Tell us how it is going for you!