I go to my local Unitarian church. We have an annual foreign policy discussion group that has now reached about 60-80 total participants and lasts 8 weeks, and also gardening, politics, musical and theater groups amongst other things.
You are so right about the Unitarian Church! That is a great place to find thoughtful intelligent people. I used to be a member of the one here. I even toyed with the idea of becoming a Unitarian minister at one time. But that was mostly because the seminary had such a great name: The Thomas Starr King Seminary. It’s like when I was in high school I wanted to be a nun, a Daughter of Charity of St. Vincent de Paul. But then, after Vatican II, like most religious orders of women, they stopped wearing their traditional habit and went into plain clothes. After that, what was the point, right? (That is humor.)
My students. It’s a very bad year when I don’t have a handful that are genuinely smarter than me, and I am no slouch. I have one right now that takes my breath away–I can only keep up with him in conversation because I’ve got twenty years on him. The random nature of students means I am exposed to all kinds of bright, passionate intellectuals, as well–rather than just people that have my same sorts of aptitudes and interests. I can’t tell you how much they teach me. And while I understand the value of deep and lasting friendships, the transient nature of the student/teacher bond is a positive: I am always getting new kids with new ideas, new experiences, new interests, new insights to share. It still breaks me up when I lose them (this year will be awful) and one or two have turned into longer-term friends, but I consider the constant influx of new Very Bright People with whom I can discuss Weighty Matters to be a huge advantage to my profession.
Not every year is like this. And I love all my kids and teach all my kids, regardless. But, oh my, those years when I have kids who want to sit in my room and talk politics and philosophy and art and history–those are good times.
If you’re not able to find another person to help you toward a mutually satisfying bout of intellectual stimulation, there’s always mental masturbation.
I was feeling the social isolation crunch after moving back to my small hometown after being away for over 40 years.
Although I don’t don’t drink these days, I found that going to the Trivia night contest at a local bar was a good way to find intelligent discussion, particularly outside with the smokers during breaks. The trivia questions provide plenty of conversation starter and the discussions often take off in very interesting directions. It’s pretty easy to spot the smart people, too.
I’m going to interpret this as a directive (including permission) to take up smoking and drinking. Thankyouthankyou! (If that’s not how you intended it, don’t tell me. 
)
You know Thelma that is a great topic and you are certainly not in a rare group. Something I have wondered recently is if a friend type group could be modeled something like AA. Use social media like facebook to get the idea out there. As local support builds just start putting together groups that could meet. AA has clubs in different cities that are run and paid for by members. Different groups hold weekly meetings and at the meeting they usually donate a dollar or two each for use of the meeting room. Club memebership is usually about $10.00 a month. Coffee and snacks are cheap. I really believe most go there for the social aspects.
I’ve been debating whether or not to answer this, but hell. Might as well.
I go to the bar. My regular early bartender is one of the smartest people I know and we have spent hours debating/discussing a wide variety of topics - my husband and I have a ton of friends that hang there (we’re all regulars) and we discuss just about anything/everything. When I get tired of the arguing (because that’s always going to happen depending on who wanders in) I go home and drink and talk to my husband. Or watch Dragnet. Depends on what time it is. 
Wikipedia. When I find an interesting topic, I read everything connected to it. I read about 150 pages/hour so I can usually finish a medium sized topic within a night (e.g. all the shows on Adult swim.) Longer ones usually take a week (e.g. all Marvel comics superheros, all DC supervillains, etc.) TVtropes is also good for getting a huge amount of information compactly, but I’ve had problems with viruses there.
Texas. I’m not exaggerating, but am probably guilty of cherry-picking the conversations a little. I’m referring to my workplace, which is governed by, and managed by sports nuts. At one time I actually encountered someone who had similar hobbies to mine (camping, etc.), but we would *literally *be scolded for wasting 10 minutes discussing destinations, by the same boss who had (also literally) just spent 45 minutes in loud hallway arguments about the Cowboys.
Once (I swear I"m not making this up) I was quietly telling a fellow dad about my kid finally getting his first job as an airline pilot. I thought it was interesting that he’d managed it at 23, and my co-worker was curious about which airline, what plane, etc. Less than a minute into the conversation, Alpha Sports Boy stepped between us, cut me off, and loudly began talking about a draft pick (or trade, or something).
My best guess about the phenomenon is that the sports fanatics don’t actually *do *anything, they just watch. My conversations and hobbies are things I actually do, and they are uncomfortable with it.
Wikipedia & TVTropes are consistent places I check out regularly. I religiously check Houzz for house porn & permies.com for permaculture stuff: gardening, earthworks & alternative building projects.
I like to read & study things a LOT more than I like to interact with people. The hubby & I are introverted by nature. We hang out in various forums more than anything.
I have a few “single-serving friends” (Fight Club) in that they are narrowly focused on a hobby or 2 & are the go to friends on that particular topic. We’re both happy if we don’t interact any deeper than that. The exceptions are hardcore sports & gun nuts. We have absolutely nothing in common there.
The hubby & I don’t have kids so it’s hard to stay friends with people whose lives revolve around their kids.
Sorry, but investing in friendships is a 2-way street. Call us when they’re grown & out of the house or are away on vacation & you guys want to kick back & have some fun.
The last group that I don’t care for in the slightest are the people who live in Meme-land.
If I have to hear how much you knuckle-draggers love bacon, Brony crap, anime, “your argument is invalid-dinosaur/shark w/ lasers” crap & the like… into the woodchipper! Now! At least you’ll be useful as fertilizer for my garden.
Be warned: there’s a window of a few years when those friends are available…until the grandchildren arrive. Then the friends disappear again. For good.
My wife, my now adult children, my partners at work and sometimes my other co-workers, pretty much anyone I consider more than the most casual social acquaintance including my best friend from med school with whom I try to keep up some, here.
I’m not so smart that I can’t find adequate intellects all around within the circles I travel, quite a few much smarter than me and just as intellectually curious, and I can learn something from most. And my circles tend not to be so sports nuts.
Lucky on all counts.
I love Sudoku. I’m not terribly good at it, but it definitely exercises my brain.
My mom, who has had multiple strokes, swears by crossword puzzles.
I think the simple act of reading helps too, even if you’re not reading anything more strenuous than Entertainment Weekly.
Taking classes can be a great way to stay intellectually active, depending on the subject.
Or, how about a new hobby? I know when I was learning to knit, that was pretty challenging. Not just the motor skills part of it, but the vocabulary, and learning to read patterns (particularly charts).
Computer and video games can stretch your brain, too. You ever see some of the strategy guides for some of them? Those guides are huge! Damn. I’m trying to play a game, not learn physics or something. 
I read threads on the Straight Dope. Anything that comes up that I don’t know, I look it up and learn something new.
I look at news articles on Reddit, particularly the science section. Anything that comes up that I don’t know, I look it up and learn something new.
(Don’t tell anyone, but I also like to read readers’ comments. Sometimes you can find a nugget of intelligence buried there.)
I read lots of nonfiction and watch lots of documentaries.
Occasionally I will go to lectures at my local university.
I don’t enjoy engaging people directly for intellectual stimulation, though. I like relating to people in a jocular, light-hearted, superficial way. Nothing deep or likely to involve debates or serious discussions. There’s a guy at work that I trade cool science articles with, and the two of us will often get into playful discussions about what kinds of crazy mad science we could do if we had a million dollars. But even this gets old after awhile. Maybe one day I’ll find someone I feel comfortable being “smart” around.
ThelmaLou, I am saddened to read your OP. You are missing out on so much joy.
To answer literally, I find stimulating people mostly at work, and I think being adventuresome in conversation, taking risks, and being warm and vulnerable, seem to be the things that help me discover what is stimulating about them (and them about me). There are interests we might share professionally, sure, but for the most part I’m talking about sides of people that aren’t at first glance noticeable in their work. Though, the integrated people themselves are bringing all of this to work in a sense. I have found more stimulating people during my 50s than I can remember finding in my 20s, and making good friends as a college student and holding on to them has not mattered in my life. For one thing, I have changed a great deal (in directions I like).
One thing that seems to have helped was reading the book “Quiet” by Susan Cain, which clarified for me that I am a strong introvert, and that I enjoy a tightly interrelated constellation of personality features as a result (turns out they aren’t a bunch of unrelated defects I should feel guilty about not fixing). One of these is that I am highly social and intensely enjoy other people in extended, focused conversations, but definitely only one person at a time, and typically with other introverts because of how they also enjoy me. It turns out that recognizing how the best relationships form for me has naturally caused more of them to form, when that wasn’t even a goal.
I’ve also had some very deep and intense conversations at PFLAG meetings (that’s Parents, Family, and Friends of Lesbians and Gays), at Alcoholics Anonymous meetings, and at meetings of an organization of African Americans who are also “Human Resources” professionals. I’ve also learned a great deal more recently about feminism in a broader context of social justice and intersectionality, and this has triggered one of the most stimulating relationships I’ve ever had, not as a single topic but as an entry to all kinds of things. I’d have to say the last 5 years feels like I’ve received more stimulation, without even trying for stimulation per se, than in the previous 20 years.
The few times I have interesting and stimulating conversations are when I go out drinking with my dad. This is rather odd since he is very religious, to the point of being almost a creationist, and I’m not. We have great talks and rants about politics, sports, history, films and even video games.
Outside of that though, I’m not close to anyone particularly intellectual. Most of the intellectualy-minded people I know are too neurotic or full of themselves for me to get along with closely.
Napier, I do easily make personal connections, ask interesting questions, engage people, etc. No problem there. What I miss is the kind of intellectual stimulation that you get in college, or around people who read a lot and widely, people who are curious and questioning and interested in stuff IN ADDITION TO the regular events that go on in your own life (family tangles, cute pet stories, daily life events). I want to hear all the cute pet stories and how your mom was when you visited her in the nursing home and about your prom night 40 years ago-- I really do. I love all that stuff, and people DO tend to tell me things. But I also want to know what book you just read, what you heard on NPR, how that *thing *that happened *there *got you to wondering about something else that you just read/heard/thought about.
Seriously, trivia night, outside, with the smokers.