Geek culture is currently going through the same identity crisis that hacker culture did in the 1980s. This pattern always repeats: first a word identifies a fringe culture, then more and more people start identifying with the fringe culture out of a desire to be "cool," then finally the mainstream takes the word over and the word ceases to mean anything because everybody claims they're it.
Take for example, the people who call themselves "geeks" just because they've... seen Star Wars. No, I'm not kidding.
Friends 'n' neighbors, it is true that many geeks are also science fiction fans. And Star Wars barely qualifies as science fiction at all - it's actually a shoot-em-up adventure set in space. But how can watching Star Wars make you a geek? The Star Wars franchise is one of the biggest entertainment franchises in the world. It blasted dozens of box office records when it came out, and still does. Currently it's the third-highest-grossing film series in history behind James Bond and Harry Potter. You're telling me everybody who saw it is an instant geek? If so, then the word 'geek' has ceased to mean anything.
We won't go into what exactly makes one a geek here (hint: it has something to do with knowledge, learning, books, skills, and technology, but not fandom). If you are it, you know it. And if you're looking for it, you know it. And that's the focus here: for young singles starting out with dating, or for geeks looking to socialize, they want to find where the real geeks hang out. Where are they going to go in today's market flooded with wanna-bes?
So here's some pointers to places where the original geek culture is still alive.
Where to find geeks:
(And as always, you may disagree with my picks. Who said I was an expert? Nobody. But nobody else seems interested in doing this, so I'm better than nothing.)
Advogato - Just celebrating its tenth birthday, Advogato qualifies by virtue of being one of the oldest social sites on the web, and by having its original focus be on technology first. Why should we look for older sites when finding real geeks? Because early in the technology adoption lifecycle, the innovators are the geeks.
DeviantArt - It looks like I'm breaking my own rule here already, doesn't it? But I'm not. I am not saying that all artists are geeks. Rather, geeks and artists may sometimes overlap. Especially if you look towards digital art, such as 3D graphics and CGI. DeviantArt has an unusually high concentration of geeks, partly because it started out hosting skins and theming packs for software.
ElfTown - Here again, not everybody into Tolkien or anime or manga is a geek. And not every artist is a geek. But when you have a community built around artistic works with a fantasy theme, you're boots-deep in geek country, and you're more likely to find geeks in the crowd than you are at, say, the mall.
Epernicus - Now we're talking! This is a social site for research scientists. PhDs and MDs. Based in Massachusetts. Everybody here would qualify as a "geek" in the general sense, although that's kind of damning them with faint praise! Please be respectful if you do join, as it's mainly a professional site for trading and sharing scientific information and resources, not a dating site. You, of course, should have a degree to join in the first place, so there you go.
LibraryThing - Not all bookworms are geeks. But all geeks are bookworms! Or at least, I have yet to meet a single, solitary true geek who doesn't read at least twice as much as the average population. That's not too difficult to do; the average population doesn't read at all after graduating school. Here's a social website devoted to avid readers. Bingo!
LiveJournal - I'll barely, barely recommend LiveJournal just to say I included one blogging network. Of all the blogging networks, you find a slightly higher concentration of geeks on LJ, mainly because it's kind of a walled garden, and because it came along (ten years ago) at the right time.
Research Gate - Just like Epernicus (see above). Same rules apply. Much newer, but has attracted over 100,000 researchers from over 190 countries.
Slashdot - With the banner "News for nerds, stuff that matters," Slashdot has tried to stay true to geek interests since its founding (it's also 10+ years old). Unfortunately, it is in the front-and-center spotlight for geek gathering places on the web, so as a result it hosts just as many flakes as geeks. Plus trolls, asstroturfers, and random yokels. Read the user's journals to aid in true geek detection.
SourceForge - Here again, not all programmers are geeks. But there's such a high crossover that they might as well be. Certainly, all open-source developers are geeks by some definition. This is a site for work, not socializing, but you could always join and offer to draw some icons or write up some documentation for some lonely geek who's behind on their project. Hint, hint, hint.
The Straight Dope - Not what you were expecting? Columnist Cecil Adams has attained a cultish following on the web, and the secret, hidden lair I'd like to direct you to is the message boards. Check through a few of the discussions. As you can see, The Straight Dope, like MythBusters, draws a high percentage of people with geek interests. Not all fans are geeks, but geeks tend to be a fan of media attractions which are focused on getting to the bottom of common misconceptions and myths using research and science.
Places I'm not including, and why:
4chan, Digg, MySpace, Reddit, and Twitter. 99% of the time, anybody using the word 'geek' on these sites wouldn't know a real geek if they came home to find one boinking their girlfriend. Posers, pretenders, wanna-bes, marketers, all. Each of these places did have a high concentration of geeks in the beginning, but that is again because of the 'innovator' and 'early adopter' stage of the technology adoption lifecycle. Five minutes after the site went public, the geeks mostly fled.
Sites exclusively about fandoms. That includes TVTropes, Star Trek/Star Wars boards, vampire movie boards, goth hangouts, and so on.
Sites revolving around related lifestyles. That includes GLBT, BDSM, furry boards, fetish sites, and sundry alternative lifestyles. While geeks are more likely to practice an alternative approach to their relationships (say, polyamory), and geeks tend to be more accepting of minority sexual identities, these cultures do not have a notably higher concentration of geeks than, say, the mall.
I'll give a tiny, tiny recommendation on the side for the BDSM subculture, because it does take an engineering brain to do those complicated knots, make home-made floggers, and craft wooden racks safely while having an understanding of endorphins and detailed knowledge of psychology. But I've probably ruined the geek ratio already just by mentioning it here.
Sites trying too hard to market to geeks. Look, if enough people with money in their wallets came out saying that they like to swim naked in napalm, 100 businesses would start up tomorrow saying "We like to swim naked in napalm, too!" That doesn't make it so. So with that in mind, look out for asstroturfers.