Windows Presentation Foundation -
MSDN - The starting place for all things.
Lawrence Moroney - Great DPE resources. He wrote the book on WPF.
NY Times Reader Info - One of the first commercial available WPF applications
Silverlight -
Silverlight.net - Pretty much the definitive source right now.
Michael Scherotter - One of the best field resources in Microsoft.
ET Online - Developed by one of my favorite customers - CBS.
AOL Social Mail - One of the first sidebar applications to use Silverlight.
Tim Sneath - A great resource for announcements and internal information on Silverlight
Expression Blend -
BlendTips.com - From the authors of the Expression Blend Bible
Media Center -
The Media Center Show - Probably the best resource on the net right now for MCML development.
Channel 9 - Some good articles on Media Center
Charlie Owen - http://blog.retrosight.com/default.aspx
Chris Lanier - http://msmvps.com/blogs/chrisl/Default.aspx
Media Room -
Media Room - A complete overview.
HDi -
MSDN - An overview of HDi development.
Amy Dullard's Blog
MSDN - HD-DVD Section
Peter Torr's Blog
Andy Pennell's Blog
XNA -
MSDN - Full overview of XNA development
Rob Cameron - One of the members of our team who focuses on XNA and Mobile development
Windows Media Services
Windows Media Services 2008 Product Page
Technet Section
Vishal Sood - Product Manager IIS