I have the same problem, but for me the context is sharing articles across different sites on a corporate intranet.

You will find that almost every DotNetNuke module is written to isolate each portal's (site's) content from all others. Very few modules are written to allow content created in one portal to be seen/altered in another portal. This is not because of any technical issues - the module will store all content for all portals in the same set of tables in the database - it is driven by the traditional "use case" for DotNetNuke. Most modules and the DotNetNuke framework itself are designed to isolate portals from each other because each portal may be owned by a completely different organisation or individual (for example in a shared hosting environment).

My solution has been to have one portal as the master repository of articles, and then share them onto other portals using the Inventua Shadow Module for DotNetNuke. This creates a read only copy of the module on the "master" site. It works but with several limitations:

• It only shadows certain types of module, e.g. core Text/HTML and Bonosoft Multi Page Content work perfectly but Efficion Articles does not display at all in the shadow copy.
• Hyperlinks in articles in the master site that point to other articles in the master site still point to the master site when shadowed. Obvious but not always what you want.

Other solutions for sharing content I have looked at are: Content Sharing (CS) module (can only shadow a limited set of modules) and the Engage Article Management System (advanced article management, not sure if this does cross portal sharing out of the box, but as Engage say they usually sell the module through a consulting arrangement you could get them to customize it).