1. Kubernetes and Prometheus.
2. Linkerd, rkt, CNI, TUF, Vitess, CoreDNS, Jaeger, Envoy.
3. Spiffe, Spire, Open Policy Agent, Telepresence, Harbor, TiKV, Cortex, and Buildpacks. See more here: https://www.cncf.io/sandbox-projects/.
4. Committees are there to define meta-standards and address community-wide issues.
5. It's a great way to understand the core concepts and inner workings of Kubernetes. It's a fun way to meet other motivated, smart people. Lastly, Kubernetes, at its essence, is a community project, and relies on the contributions of its members and users.
6. SSH keys and SSL connectivity.