I used to game a heck of a lot, just go into a gaming server play their for a couple of days, get to know the guild be nice and ask them if their is a website where you can sign up.
I used to be in an Americas Army clan for ages quite a while back (when i was about 13/14) and you just have to have a laugh with the people on a server, get to know them, be nice and ask if they have a teamspeak you can join.
its how i mostly got into guilds/clans.
If you want an online community then World of Warcraft is a good choice, however it can become addictive.