As an atheist, I do envy the religious people their weekly meetups!

It's true. I'm a chuch-goer and have a couple of board gaming groups going from people I met at church. I've met all kinds of people at church that I probably wouldn't have met otherwise. There are computer chip designers, software engineers, accountants, doctors, police officers, a navy seal, a lumber mill operator, professors, scientists, veterans living at the local salvation army center, psychologists, business people, economists, etc.

Trivia works. I go to two trivias (M/W) almost every week. I have a group of about 6 people that show up (random which subset) to each (not the same people) to play on my team, sometimes more (used to be a lot more but some people moved). And the other teams are people I knew before going there or have come to know since starting. Pleasant way to spend a couple hours a couple times a week. A bit of hanging out, a bit of competitive fun, and more hanging out.

Can you just randomly drop in solo or with another person to a trivia night? I've been to a few, but only ever as a sub on an "established" team.

I'm pretty welcoming and gregarious, I have had random people join my team before when they asked (my teammates were less comfortable at first, but relaxed and welcomed them later). This will definitely depend on the crowd. It may be easier to start your own team (or playing solo at the bar) and just start getting to know the other teams for a while first before asking to join them.

It also depends on the location. One is a restaurant, people are generally less welcoming to random folks sitting at their dining table (unfortunately). The other location is a bar. It's much easier to just join a random team. Find 3 people sitting at the bar and ask if you can join them. Or, like the last folks that joined us, find a table with several empty seats and ask to join them.

Join a club for people with common interests. Or find a new interest - I started CrossFit 2 years ago with no prior interest in fitness and to me the social aspect is as important as the fitness aspect, if not moreso.

Of course, there are non religious social activities.

But none that are so completely unforced where you can just show up once a week for no reason and be welcomed. Or so it seems from the outside.

There was a weekly freestyle dance in New York City that I attended, many years ago. In a studio, with a good wood floor, near Broadway and Houston. It was run by a collective, and part of a northeast association, which had summer dance camps. As I recall, it cost $5 at the door, and less if you subscribed. All ages were welcome, even toddlers. Maybe it still exists. And there are many others, for different dance styles.

Meetup.com might have meetups for people you might find you have a lot in common with

Meetup.com has issues. Their recent site redesign pushes people not to be loyal to groups and use it as a "what can it do for me right now" It's killed group identities and there have been a loss of groups. (Orgs have complained very loudly.. but meetup doesn't care)

I've seen this happen in my group and we're looking to see what's next.

For most of us hacker-types, that's a good role for hackerspaces to fulfill!