DotNetNuke is an open-source Web Application Framework ideal for creating and deploying projects such as commercial websites, corporate intranets and extranets, online publishing portals, and custom vertical applications.  DotNetNuke is a ASP.NET application which is hosted on Microsoft Windows Servers and Microsoft SQL database.

The Virtual Sign Post runs on DotNetNuke.
DotNetNuke is expandable with modules which work like individual applications.
DotNetNuke can be "skinned" providing you with almost limitless visual possibilities.
DotNetNuke handles your security with user ID creation, profiles, custom groups, and permissions.