In addition to all the players mentioned previously, there is a set of complementary SIGs that meet regularly to discuss issues and opportunities from within a given focus area of the Kubernetes ecosystem. From within those SIGs, there are sub-bounded working groups that aim to accomplish a specific goal. There are also sub-projects that further cut up the interest space, and committees, which are there to define meta-standards and address community-wide issues.

Here's a list of the current SIGs in operation, with the current chairs and meeting schedules:

If you'd like to join one of the meetings, check out the master list here: https://github.com/kubernetes/community/blob/master/sig-list.md.