It is a fact that being surrounded by people that have the same interest as you is a blessing, whether online or offline. At least you get to relate with them on a deeper level.
No, I don't belong to any, but I have a couple of friends who are designers that I speak to whenever that I am stuck on a project and they've always helped when I needed them.
I belong to Deviantart community which counts as a graphic design community to the best of my knowledge. There are so many skilled graphic designers in that community.