We use IRC and email as our primary means of communication.
We can be found in #docs on irc.gnome.org. This is the place to contact us if you have quick questions or need help writing a patch.
For the development of documentation-related tools, we use the firstname.lastname@example.org mailing list. This list is for programmers and contains technical discussions. You can subscribe or read the archives.
We had a project blog but it seems pretty dormant these days.