What are your thoughts on using Windows Live Writer communicating with your website as the content editing system?
Windows Live Writer supports multiple category blogs (i.e. can be news, articles, and blogs), multiple category pages, tagging, XHTML WYSIWYG editing, image and file uploading via services or ftp, and the client has a "Insert HTML" plug-in library with a lot of already developed plug-ins for popular sites.
The trickiest part is implementing all of the XmlRpc methods in your services, but some digging with Reflector has exposed them as being pretty simple to implement the features.