The Microsoft Advertising SDK was only available in the US for the initial Windows Phone launch. With the release of Mango however, 11 additional countries were added including the UK.
What does this mean? It means it’s really simple to integrate advertising into your Windows Phone application (or game, Silverlight or XNA). Microsoft Advertising Network servers deliver ads to your users and you get a share of the advertising revenue.
In-App advertising can offer a great alternative mechanism for monetizing your apps. Instead of charging up-front, you offer the app for free and make money through advertising. Or you offer a free, ad-supported version alongside a paid, ad-free version. Experimenting with different models may itself prove to be a very worthwhile investment!
Mike Ormond has written a quick post on how to implement the Ad SDK into your Windows Phone Project.
Full Article: Mike Ormond's Blog