Free ASP.NET CMS: Umbraco
Licensed under MIT, Umbraco is a free and open source asp.net content management system, which is written in C# and deployed on Microsoft based infrastructure. As one of the leading .NET based open source CMS systems, Umbraco is easy to learn and use, making it perfect for web designers, developers and content creators alike. You can run anything from small campaign or brochure sites right through to complex applications for Fortune 500’s and some of the largest media sites in the world.