Xamarin is offering free subscriptions to published Windows Phone developers, as long as you sign up before August 31. Normally, a Xamarin subscription could cost $99 per year.
If you’re unfamiliar with Xamarin, it’s the service that allows developers to write an app in C# and create an app for Windows Phone, Android, and iOS. It’s a pretty nifty tool for developers, especially independent developers that don’t want to have to write three apps, one in Objective-C, one in Java, and one in C#.
Those independent developers appear to be exactly who this promotion is aimed at, as each developer account can only get access to a single subscription, which includes access to Xamarin’s Visual Studio tools.