The majority of Android developers use Java to create their apps. While Java isn't the hardest programming language to learn, it's always best to get as many people developing as possible.... not that Android is hurting in that respect. Even so, a new way to create apps using Microsoft's familiar C# language is now available, by way of TallApplications BV's Dot42 - a tool that aims to accomplish this task without requiring something like mono.
The gist is simple: it's a compiler that will allow you to code apps in Visual Studio. You can use existing Android API libraries. There's even limited support for editing String and Menu resources in WYSIWIG. Unfortunately, due to technical restrictions, Visual Studio Basic is not supported.
The community license will allow you to use Dot42 in your own projects for free, but creating commercial apps or publishing to the Play Store (even for a free app) is prohibited. The professional license is a pricey $649/€ 499.00 per developer, with a 25% discount for packs of four. Each license comes with a year of priority support, with subsequent years costing 30% of a license, with free major version upgrades as long as you're subscribed.
So, any developers interested in giving it a go?
Update: The Dot42 licensing policy described above has undergone a significant change. As noted on Dot42's website, free apps can now be published to the Google Play Store and other marketplaces without violating the community license. In addition, the price for the professional license has been lowered to $399.