This may be old news to some of you, but
the beta of Office 2007 includes a new feature that lets you author blog posts, and post them to any server. It generates clean, efficient HTML, contrary to Office 2003's "save as HTML..." option. It provides a streamlined user interface, when you are creating a blog post, eliminating the UI things that you aren't gonna need. And it supports ATOM and the metaWeblog API, so it will work with Sharepoint 2007 blogs, telligent's Community Server, MSN spaces, as well as Drupal, WordPress and MT. Nice!
Read More here.
This isn't exactly interop between .NET and something else, and so maybe it falls outside the purview of this particular blog. But it is nice interop between Microsoft systems and other systems, so that qualifies this bit of news for inclusion here.