Most of the discussion happen on IRC on the #fedora-modularity channel on Freenode.
Use the main Fedora Development list, prefixing subject lines with [Modularity].
Have a look at our Pagure Modularity group and our GitHub Modularity organization.
The Modularity Working Group meets once every two weeks to discuss, post updates, and make dedisions.
This is where you ask the Fedora Modularity Team questions (and we try to answer them)!