MSdev has a great series of video trainings to migrate existing Android developers to Windows Phone 7 development.
The inaugural video features host Bill Lodin and his trusted whiteboard animated partner talk about Windows Phone 7 for the iPhone/Android developer. From downloading free tools to deciding the type of application you want to create, to connecting to services in the cloud and placing your app in the Marketplace, Bill gives iPhone/Android developers a look into the steps they can take to add Windows Phone 7 into the development workflow.
Further videos in the series explain specifics elements of application development and also the migration of an Android application to a Windows Phone 7 application.
The other two videos introduce programmers who are familiar with using the Android Development Tools (ADT) with Eclipse to Visual Studio 2010 and also a comparison of the programming languages used in Android and Windows Phone 7, Java and C#.