Today we published the final v1 spec for Simple Sharing Extensions, under a new name, FeedSync. The new name is a little simpler than the old one (kind of ironic!) and it captures the intent pretty well.
Sam Ruby was kind enough to update the Feed Validator for the changes. Thanks Sam!
The FeedSync site has pretty much everything you need to get going, but if you're looking for more, let us know what's missing.