Just giving a shout out to the organized "official" groups and clubs that I've jumped into. First since this is an online post would be TheFreeBootaz; It's a paid forum, but the price keeps things extremely civil and certainly weeds out the trolls who love to hide behind anonymity. That forum is from the 40k Radio team at TheFreeBootaz forums. It's probably one of the best forums I've found in the hobby yet, parsed down to quality debates and discussions.
If you're the kind of person who likes to sit down at the local club and just banter about the hobby, or things going on outside of the hobby this makes a great forum. It's a social place, so expect your welcome to be responded to within minutes, and to be very warm indeed.
For those who prefer a little face time and are in the White Plains, NY area then I'd highly recommend my local club "Battle for Salvation" as an in person version of the forums. As with the Bootaz a warm welcome was made for me within a few visits. Really glad to meet all the crew there and will continue playing, painting and hobbying with them as long as they'll have me hangin' around. :)
Glad to be part of this hobby community over all, and if you aren't local to a club get on to somewhere and just share what you do! Have fun finding new people to share with, it's a sure fire guarantee to help you get more fun out of your investments.
So, if you're in the White Plains area check out Battle for Salvation (The link is to the GT, but the head of the organization Bobby can be reached there for more information)
and if you're not in the area, but want your hobby fix take a look at The FreeBootaz