MCE WPF Application and Article -- Impressive Prototype!
Casey, from brains-N-brawn, has written an article that describes his experience with Avalon and MCE, along with the Windows Media Player SDK. His inspiration is largely a cloning exercise -- you can read the article to find out the details on what he's cloning. The article has lots of screenshots, videos of the application working and, even better, the source code! Take a look!
One of the things he does in the application (and describes in an article) is creates a way to play .wav files other than using the MediaElement using the System.Media.SoundPlayer -- he hit some bugs here but worked around them with some clever asynch tricks.