Different Drupal 8 core initiatives used different tools to achieve their goals, some of the most common tools included:

IRC meetings at set times
Google Hangouts
issue tags of different kinds (eg. the sprint tag)
heavily organized sprints
http://drupalofficehours.org/
http://vdc.drupalofficehours.org/
groups.drupal.org
http://drupal8multilingual.org/
We wish we'd have tools as rich as envisioned in http://groups.drupal.org/node/144584 but we mostly needed to turn to our own solutions for what worked for our initiatives. What can we learn from these tools and approaches and what kind of improvements would be ideal on Drupal.org to help teams work better.

This is targeted to be more a discussion than a presentation so do not expect leaning back and reading slides all the way.