At the last FediForum, we got the #Fediverse #Developer #Network started.
If you don't know about it, it's mostly about half dozen Matrix rooms where a lot of Fediverse developers hang out and discuss matters they care about, from highly technical interop problems and best practices for implementing the Fediverse protocols, to how to talk about and market the fediverse.
We also have a website and had the occasional video call for show-and-tools and face-to-face discussions.