DotNetNuke 3 Beta 3 is available for download
DotNetNuke is an open-source community portal written in ASP.NET, DotNetNuke is popular enough to warrant the existance of a number of third party services, we have used it for communities like http://panama.latindevelopers.net. A couple of days ago Beta 3 of version 3 was released, offering a number of enhancements like multiple portals with one codebase/database and separate upload directories. So go download it and give it a try.