I live and breathe Google Answers. It has quite literally become the focus of my waking life. Most people I encounter (even on the Web) have never heard of it.
Some things that I’ve personally noticed…
The local music scene: I used to see live shows every weekend, and was always in the know for what cool acts were coming to town. I burned out around 5 years ago and found other hobbies. I picked up a local arts paper the other day and didn’t recognize a single artist or band, and most of my old favorite clubs were gone and replaced with venues I’d never heard of…
Sports is another. I used to be a sunday-football and weeknight-basketball watching guy, plus world cup, NHL, NCAA, you name it, I loved watching sports. Then, I abruptly stopped…the luster and interest was gone. I haven’t watched a pro-game for 6 or 7 years now, and have no idea who has won the Superbowl or NBA titles for the last 5 years.
I think just the massive time allotment required and active brain space for the sports and music hipster scenes was just too much, and my brain rebelled. I picked up other hobbies that I’d wanted to explore, and haven’t missed any of the old days.
No, Gorean as in “Gor” the planet Gor. They’re kind of a subset of BDSM. I say kind of because there’s a lot of non-BDSM stuff involving honor and so forth that come from the novels of John Norman, author of Gor. They’ve got quite a few websites, and some RL folks. They are pretty darned obscure but the ones who participate in it often get involved enough to easily fulfill your "fill your world’ requirement.
OK, what is Google Answers apart from Google and why should I care? Why do you care?
Know any good websites? I did a little Googling last night but couldn’t find any clear statement of what the movement is about. Even Wikipedia doesn’t have much info.
Would easily fit into the OP.
I am a member of APICS, there is a pretty large membership and educational support base for it but if you are outside of the world of materials management you probably would never hear of them.
Well I can say that at work the other day I made a joke that riffed on the “Goes to 11” fromThis is SPinal Tap. Got back a blank stare and the guy explained to me he had never seen the movie. So I get somebody from a neighboring cubicle and he also says he has not seen the movie. Flabbergasted I go get someone else nearby and THEY say they haven’t seen it. I have to go through 5 people before I find someone who has seen the movie.
I have a good example.
I’m a professional magician, and a lot of my life (but not all of it!) revolves around magic, magicians and magic shows or events. There are magicians (amateur or pro) everywhere in the world - wherever you are, and whatever you do, I’ll bet you’re never more than 50 yards away from an amateur magician. We have meetings and conventions ranging from small, local events to international gatherings for thousands of people. If you wanted, you could spend more or less your entire year just attending magic get-togethers and events held all over the world. There are thousands of magic books, tapes and DVDs, and every year several dozen more get created. Magicians are also very sociable. Wherever I may travel in the world, I can plug in to the local magic ‘network’ - I get to meet new friends, get taken out for a drink or dinner, get taken to shows, invited to people’s homes and so on, just because of a shared love of magic.
But if you aren’t into magic, all of this is more or less invisible and un-noticed.
I hope you give the answers. I can’t see how someone can get addicted to paying people to answer his questions.
That movie was rated one of the top 10 cult movies of all time by Entertainment Weekly, if not number one.
Another movie which has many die hard fans but most people never heard of is the sick and twisted cult classic Pink Flamingos, which had to be written and directed by the equally twisted John Waters.
Also, how many people have heard of Web Comics? Especially the insanely funny only to people who like to talk about video games; Penny Arcade.
Unix
Webcomics are mainstream on the internet.
That one works in reverse. Sure, the people who aren’t having it know very well that people have it, but I think most of the people who are having it would be absolutely stunned by just how many virgins there are out there. And by choice no less. 
I wouldn’t be so sure. I love telling the story of my friend who had somehow managed to go his whole childhood without seeing any of the Star Wars movies. Finally I dragged him to see Episode 4 when they released the Special Editions. He fell asleep in the middle of it. But a few years later I decided to take another stab at it, and got him to watch Empire Strikes Back on video. We got to the pivotal scene, and Vader said:I am your father To which my friend responded with an astonished (and entirely genuine) shout of "Oh my God!"
Try here. Registration is mandatory, but free. This is mostly for those who are into the serious aspects, not the BDSM-with-an-extra-kink bit.
…And behave while you’re there, or I’ll bust your butt 
Sport; I really don’t have the time for it, except for a few things like downhill skiing (which I watch for the spills) and… I dunno… obscure stuff like curling; mainstream sports like football(soccer to you) just turn me right off.
I was in the supermarket one time and the checkout girl asked me “who do you think will win tonight?” - it was terribly embarrassing because I didn’t even know what sport she was talking about (could have been football, rugby, cricket…)
This discussion reminds me of one of my favorite lines in the movie Diner.
“My name is Jane Chisholm, like the Chisholm Trail.”
“What f*cking Chisholm Trail?”
“Do you ever get the feeling that there’s something going on that we don’t know about?”
Role Playing Games in general. I hang out with a small but dedicated band of gamer geeks, and we tend to play 1-2 times a week. I begin to realize, however, when meeting other people, that sort-of alienation. Hard to bring up other topics, because it’s a hobby that outsiders really just kind-of look at you like you have a second head when you talk about it.
Also: Math. I don’t know if it fits or not. I have a very good brain for math, and I -love- doing practical applications with it. If the shadow of a tower is the indicator of where the burried treasure is, where will the shadow fall on x day at y time? I -thrive- on doing that sort of problem, as well as other tidbit-y types of math. Other people don’t even seem to understand that such problems can be done without expensive software, and just sort-of look at me, mouth agape, when I do it.
Google Answers is a service where a person can post a question on almost any topic and offer a fee for the question to be answered by one of the service’s official contractors (called “Google Answers Researchers”).
Why do I care? Because Google Answers has been my sole source of income for three years. Why should you care? Dunno. You might browse through and see if anything strikes you as interesting. I would think that Dopers would find the place to be fascinating.
Has anyone mentioned MySpace yet? You wouldn’t know it, but that thing is huge.
There is no single website that I would say defines Gorean beliefs and practices. It kinda sprang up online and then went RL in most cases, though I’m sure there were some people who read the Gor novels and then said, “That’s for me.” There’s no one who says what’s Gorean and what’s not – well, actually, there are a LOT of people who say that, just no one who is an acknowledged leader. John Norman, author of the Gor novels, didn’t really support the Gorean community in the way that, say, L. Ron Hubbard did. He’s corresponded with them, but I don’t think he’s all that online. Could be wrong, it’s been a few years since I checked. Basically, his attitude seems to be, “Sure, you kids play with it all you want.”