Earlier this week Dries Buytaert wrote about CMIS a proposed standard to enable interoperability among content management systems. And in that article he said he wants to "push harder" for Atom as a default output format for Drupal so that Drupal be CMIS compatible in the future.
At Drupalcon Szeged Peter Wolanin (Dries colleague from Acquia) presented a talk "Page serving and rendering (XHTML/XML/JSON, etc.) - now and Drupal 7" in which he talked about the different ways Drupal may go about rendering output in formats other than (X)HTML.
