Of all the Open Source projects out there, the Mono Project has got to be one of the most interesting and worthy. The goal is to create an open source version of Microsoft's .Net Common Language Infrastructure (CLI or runtime to you and me) along with compatible class libraries and a C# and VB .Net compiler.
I think it will be fantastic if they succeed. For one, it will legitimize the .Net programming model to a wider developer audience and make it more pervasive. I still believe .Net is one of the best technologies out there and I'd love to see the Open Source movement adopt it. This broader adoption would foster more language and library innovation.
While it might help Microsoft in some ways, it would also be a huge boost to Linux and the Open Source movement. More Open Source projects would run on the Microsoft platform while commerical Windows applications might find their way onto Linux. It breaks down the platform barrier. This was the risk Microsoft took by giving the core of .Net over to a standards body. Innovation and competition would move into the class libraries.
The main backers of the Mono Project are the developers behind Gnome. Rather than winforms, their UI library of choice is GTK#. Interesting to note that Mono and Gnome are part of the Novell strategy (Novell? Yep, they still exist). A Mono Project Roadmap was recently released. The first official release is scheduled for Q2 2004.
I'm really looking forward to it.