I just got an email from Microsoft about the new Visual Studio 2010 launch among other things. Also in the email was an article about Mono. I think some people find it hard to believe that Microsoft supports the cross-platform implementation of the .NET framework, but here it is. Microsoft actually does support Mono. This is from the email:
The Mono ProjectMono is a free and open-source implementation of .NET that runs on Windows, UNIX, and Mac OS. In more than 5 years since the first version of Mono was released, the Mono project has continued to add support for new functionality, such as C# 3.0, LINQ, and Silverlight, and has continued to see adoption. Come hear about the latest developments and future plans from the founder of the Mono project.
They don't go as far as to mention Linux, but they do mention Unix. I'm surprised to hear that Mono supports Silverlight (!?).