Just wanted to point you all to two great screencasts on how you can develop applications on Windows Media Center. Personally I love Windows Media Center, it is the center of my entire home entertainment experience, it is networked and streamed all around my house. My wife at first was not interested, but now she cant live without it.
I think this is a great platform for consumer focused applications, and would love to see what the general public can come up with on this platform. Check it out at the following link.
Windows Media Center Sandbox - Screencast: Creating A Simple Media Center Application