I've been working on a new project called Klaxon: it's a G-Sensor enabled alarm clock for Windows Mobile phones. One of the features is that it can allow playback of MP3s and WMAs. I initially wrote the application in .NET 3.5 assuming that the new System.Media.SoundPlayer class would support those audio formats. But, they don't! I ended up writing my own class that handles all the Sound related PInvokes:
It should work just like System.Media.SoundPlayer.