DotNetNuke
DotNetNuke is an open source content management application and .NET development framework.
DotNetNuke is the leading Web Content Management Platform (or CMS) for Microsoft ASP.NET, powering over 700,000 production web sites worldwide. The flexible DotNetNuke open source CMS platform also functions as a web application development framework. Depending on your role within your organization, DotNetNuke provides powerful benefits to support your Web initiatives.
-DotNetNuke developer