I came across this interesting map of the internet, which is apparently roughly to scale based on the number of people using each service or taking part in each activity.
Notice how Facebook dominates the world, with a frightening number of people playing Farmville (I don't know what Happy Farm is and refuse to look it up).
That QQ in the corner is a Chinese instant messaging service which has morphed into an all-purpose networking/gaming thing and will no doubt conquer the world one day. As it's currently confined pretty much to China we can probably close our eyes and pretend it's not there for now.
Notice the forums nestled snugly in the Sea of Memes. This gives me a chance to rant once again about forums and why they are so often overlooked when people are talking about what's happening on the internet.
If you want to find an actual community, and conversations taking place, check out a busy forum. Honestly, I think they get neglected by self-styled gurus because they were successful long before anyone invented phrases like social media or web 2.0, and they demonstrate that people over 30 were communicating happily on the Internet long before social media consultants existed.
Having said that, if you want to experience the joys of forum warring for yourself, don't go near 4 Chan (it's not as funny as it thinks it is). I humbly recommend the Something Awful forums. And if you're temped to visit MMO Isle, check out Eve Online.