I just noticed this item on Charlie Owen's blog and wanted to post it here as well.  There is now a public download available for the Windows Media Center SDK for the Windows 7 beta.  Here are some useful links:

• SDK installer location - http://download.microsoft.com/download/7/5/0/7501F066-9B35-4F9E-8A63-0957687DE1E6/WindowsMediaCenterSDK6.msi
• Media Center development forum -http://discuss.mediacentersandbox.com/
• Summary of new Windows 7 Media Center features - http://blog.retrosight.com/WindowsMediaCenterInThePDCBuildOfWindows7.aspx
• Summary of new Windows 7 Media Center platform development features - http://blog.retrosight.com/WindowsMediaCenterPlatformInThePDCBuildOfWindows7.aspx