tl;dr: http://discourse.ros.org is the latest and greatest in ROS community
communication channels. Go check it out.

Good morning,

We'd like to officially invite you to Discourse, the latest stage of
evolution in ROS Community communication.

After feedback about the failings of Google Groups and the non-open,
proprietary nature of Slack, we launched an experiment migrating the ROS
Java SIG from a Google Groups mailing list to Discourse.

We've had positive feedback so far. The forum interface is a vast
improvement on plain old email, there is support for integration with
Github, and the project is free and open source.

We would like to move in the direction of using Discourse for new SIGs and
migrating currently active SIGs to their own "Categories" on Discourse, if
the members of those SIGs are interested. If you are the leader/owner of a
ROS SIG, post in Site Feedback on Discourse if you'd like to start the
migration process.

Slack is officially deprecated: you are free to continue using it, but if
you want something to come onto the radar of the ROS team, you should
prefer to use Discourse, IRC, Github or email.

answers.ros.org remains your resource for asking specific technical
questions about ROS, while Discourse should be used for more open-ended
discussion and community organization.

Sign up and take a look around (you can use Github or Google accounts to
log in). Use the "Site Feedback" category to give feedback, including
suggestions for new categories.

http://discourse.ros.org

"Good company and good discourse are the very sinews of virtue." - Izaak
Walton