There are so many various aspects of Linux that can be dealt with. An overall Linux site (like mine and numerous others) or you can get it down to a specific OS flavor (and there are a BUNCH of them out there).
You will find that there are forums in existence for just about anything you can think of. The thing is, pick something that YOU enjoy and go from there. Me, I have several interests, and forums aligned with them. Personally I don't care if they take off or not - they give me something to do.