I'll be doing a Webinar on May 23 on the Xamarin Mono for Android Designer that is new with Mono for Android 4.2. This is a free webinar presented by AppDev, please attend if you can. 
Here is some info on the webinar:
Android user interfaces can be
created declaratively by using XML files, or programmatically in code.
The Xamarin Android Designer allows developers to create and modify
declarative layouts visually, without having to deal with the tedium of
hand-editing XML files. The designer also provides real-time feedback,
which lets the developer validate changes without having to redeploy the
application in order to test a design. This can speed up UI development
in Android tremendously. In this webinar, we'll take a look at UI
Design in Mono for Android, the basics of the Xamarin Android Designer,
and build a simple application with the designer.