The first one on our list will be the awesome Docker list.
Awesome Docker available on GitHub at http://veggiemonk.github.io/awesome-docker/. The author updates the list often, so you can clone the Git repository locally and do periodical updates to see what's new. Awesome Docker contains sections such as an introduction to Docker, tools (with the groups such as developer tools, testing, or utilities). The Videos section can be especially useful when learning Docker, you can find tutorials and trainings here. Apart from this list, it's really hard to find some more that could be useful.