I am a member of the W3C Social Web Working Group, and the editor of the Webmention and Micropub specifications.
Webmention
The Webmention specification is used to enable cross-site commenting and reactions between independent websites. The specification reached Candidate Recommendation in May 2016.
Private Webmention is an extension that supports sending and verifying Webmentions for posts that require access control.
webmention.rocks is a test suite you can use to test your Webmention implementation.
Micropub
Micropub is an open API standard used to create posts on one's own domain using third-party clients. Web apps and native apps can use Micropub to post short notes, photos, events or other posts to your own site.
The specification reached Candidate Recommendation in August 2016.
micropub.rocks is a test suite you can use to test your Micropub implementation.
PubSubHubbub
In 2016, the W3C adopted PubSubHubbub into the working group. I have contributed to the spec, and also wrote a simplified guide to PubSubHubbub.