The primary channel for important development-related discussion is the xoreos-devel mailing list. All developers should subscribe to it.
If you use gmail, be advised that gmail sometimes puts emails coming from smaller servers, like xoreos.org, into the spam folder. There is unfortunately nothing that we can do about this.
The full set of public lists are:
This is the official developer mailing lists, for planning releases, and general discussions concerning development and project management.
Commit logs, receiving an email for every Git commit.