Novell are developing a version of Mono for Google Android. Monodroid will allow developers to write .NET applications for Android phones:
MonoDroid will give Android developers tools for binding the Java APIs, while making them accessible through the JIT-compiled, 335-powered runtime engine. This will hopefully allow allow developers to reuse their engine and business logic code across all mobile platforms and swapping out the user interface code for a platform-specific API.
This appears to be similar to MonoTouch, a way to develop .NET applications for the iPhone.
I hear Microsoft have released downloadable previews of developer tools for Windows Mobile 7. Apparently the new GUI is based on Silverlight.