Have you heard about Silverlight Mobile?
Microsoft Silverlight powers rich application experiences wherever the Web works including mobile devices. Silverlight provides a homogenous platform for developers to target a large number of devices as well as deliver rich interactive applications with scalable vector graphics user interfaces and mobile-optimized media. Further, Silverlight for mobile enables developers to reuse their existing desktop code, content and skills, and leverages the flexible .NET programming model.
It's not available just yet but take a look at http://silverlight.net/learn/mobile.aspx for more details and links to some great sessions. You can also catch Amit Chopra & Giorgio Sardo's excellent session at PDC here.