I just released the free, open-source AtomSite <http://atomsite.net> 0.9 web publishing platform. This release is completely modular and it takes advantage of Atom extensions and AtomPub extensions. The AtomPub plug-in is core and enabled by default. The service document stores the site, workspace, and collection configuration.
AtomSite can be used as both a CMS and blog engine. AtomSite is built using the ASP.NET MVC 1.0 framework, just released this week. It has some really nice features such as composite widgets, a theme view engine, plug-ins, OpenID, and more. The source code is available at: http://blogsvc.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=24915 or http://atomsite.googlecode.com/svn/trunk/ Also, I'm looking for some help on the project if anyone is interested in joining the dev team. Thanks for any feedback you may have.
