Rainbow, an open-source .NET content mangement system is now at a rather mature state, and is being used in several commercial sites.
Based on the IBuySpy development kit from Microsoft, Rainbow now has over 45 modules out of the box, and many more available for free download. Pages are managed in a hierarchical form, with menus providing standarised navigation, meaning unlimited depths to the portal.
One of the really interesting aspects of Rainbow is its ability to use the many authentication aspects of ASP.NET. You can easily use your existing NT membership and roles to provide access to the portal, which makes creating an Intranet portal a simple task compared to many other CMS packages.
Rainbow also has a great 2 step publishing system. Each module can require content modifications and additions to be approved before being published.
It is this kind of fine-grain control is what makes Rainbow a serious, effective CMS which might make it a viable altenative to the mighty DotNetNuke…