Ask HN: What are some communities that self-teaching novices can join?

Often times I am hitting some walls while trying to understand the theories like concurrency models, state machines and stuff. Most of time I am not sure what I need to google to find what I want and don't have a solid question that warrants asking on SO or here. These are the times I feel like discussing these topics with someone knowledgeable would clear things up. So are there any such places where I can do that?