A couple of historical predecessors:

The scientific charity movement starting in the 1870s: https://www.jefftk.com/p/scientific-charity-movement

And John Wesley advocating earning to give in the 1700s: https://www.jefftk.com/p/history-of-earning-to-give-iii-john-wesley

To me, The Uniting Church of Australia.

It's probably controversial to list a church, but I walked in to the church and got a bible study on how to effectively help people in global poverty, and absolutely loved it.

I definitely think that Churches are a good place to start for places similar to EA, simply because I find that communities around churches have a lot of what I call "intent to do good". Particularly, In my experience, they seem to be unusually disposed to help reduce global poverty. 

Further, when coming into Christianity, I found that there are concepts that are incredibly similar to Peter Singer's notion of strong obligation to help the poor. Examples include:

• "If you wish to be perfect, sell all you own and give to the poor" (Luke 12:33)
• "What you do for the least of my brothers and sisters, you do for me" (Matthew 25:40)

I'm so convinced of this, that even though I would call myself an atheist, I still heavily involve myself with my church community in order to try make a difference in the way that people view the church, and to direct the church in ways that we can help more people.

‘Nordic school metamodernism’ has been an interesting complement and contrast to EA in my experience.

They have an active forum of people who are passionate about things like cognitive complexity, political philosophy, and societal development beyond moral relativism. They have two provocative books (dense with interesting ideas imo), the first of which was just released on Audible. In general, I find them to be ambitious, secular, sane, and attempting to make things better for all sentient beings. (The style of the half-fictional author, the great philosopher Hanzi Freinacht, has its pros & cons, though, and may not be for everyone.)

Some takeaways for me (in contrast to EA) include:
- complementing the often hyper-individualizing focus of EA;
- highlighting a ton of (often-overlooked) factors that might be possible to develop in our personal, social, and institutional matters;
- generally combating passivist misanthropy by doing a detailed & insightful tour through what things suck, how exactly, and how they could suck less in the future if we manage to actively develop all of them (i.e. inspiring people into activism in all areas of life).

I’m not up to date on what concrete things that community has done, but to be fair, it does seem necessary to first spread awareness about all those problems before tackling them. They might also be quite constrained by lack of effective coordination around their aims, which may be a main reason why not so many people within the EA community are actively even aiming to go the same way. But I think many people would already benefit from the (imo worldview-enriching) concepts in those books, if they can stand the rhetorics.

(Twitter/Reddit) Neoliberalism

A political ideology focused on free markets, regulating market failures and LGBT+ rights. This isn't necessarily the same as "Neoliberalism" which is an older ideology. The name is confusing.

Twitter Neoliberals seem to me to find EA ideas compelling but want to be part of a political community. So key neoliberal figures tend to end up recommending GiveWell and occasionally repeating EA talking points. I guess neoliberals might wonder why no one wants an EA political party. Their marketing tends to be more combative than EA.

edit I edited this to make clearer that I was talking about neoliberals on twitter/reddit as opposed to the more general label.

The vegan community. Both are ultimately about reducing suffering, and of course, EA is also very involved in animal welfare.

The main difference is that EA seems primarily interested in outcomes, and veganism is also interested in self-sacrifice and symbolism. You don't avoid eating animal products because you think it will make a huge difference, but simply because it's the right thing to do.  As Loki said in "American Gods", "The symbol is the thing". 

 Maybe the vegan community would find EA a bit icky just because it feels like EA consists of rich people sacrificing very little of their personal lifestyle but making the "right" donations to absolve themselves. 

RadicalxChange (RxC)

Pushing systemic change via new mechanisms and general activism. Quadratic Voting, "radical antitrust" (don't know what that means)

To me RxC looks like people who want to help but don't find the EA approach compelling. Some comments (epistemic status: 75%):
- They want systemic change and clearly care
- They are about bold moves and testing new ideas without the level of due diligence that EA usually requires
- They reach artists and activists (if you want an analogy, look at their stylish/garish website which is way more "out there" than any EA website I've ever seen in terms of design)
- They seem embedded in the crypto community

Maybe the John A Hartford Foundation.

Various utilitarianism- and Peter Singer-motivated efforts in global poverty and animal welfare, decades before the modern effective altruism community emerged.

Mohism.

Empirical development economics and GBD-prioritized global health interventions.

Of course, the "rationalist" and "transhumanist" communities have strong similarities, and large chunks of them have essentially merged with EA.

There are various efforts aimed at more widespread use of cost-benefit analysis, e.g. see Sunstein's book.

Systems thinking shares the question: where and how can one intervene to achieve large improvement for small investment, minimize off-target effects, and have the improvement actually stick instead of revert?

Some of the charter cities movements have a similar philosophy to EA, but with more of a focus on improving governance.

In particular, I'd guess GameB is the closest to EA since it acknowledges a lot of the same X risks EA is focused on. https://www.gameb.wiki/index.php?title=Main_Page

The Seasteading Institute https://www.seasteading.org/, which promotes floating cities is also similar. It used to run Ephemerisle https://ephemerisle.github.io/, which was apparently sort of a Burning Man on water.

EA seems to interact most with the charter city community through the Charter Cities Institute https://www.chartercitiesinstitute.org/. Their founder has posted on the forum before. 

Besides improving governance, their messaging seems to focus on widely known causes such as climate change and poverty on their site so I'm not sure how close their philosophy is to those in the EA movement.

If you're interested in charter cities I'd also check out 2 new one's in Honduras: 

1. Mariposa https://mariposa.hn/
   1. Scott Alexander writes about it here: https://astralcodexten.substack.com/p/model-city-monday-8221 
2. Prospera https://prospera.hn/ 
   1. Scott Alexander writes about it here: https://astralcodexten.substack.com/p/prospectus-on-prospera 

I like the answers so far. I'll add a few more:

• Professional Futurists
• Wisdom -- Awakening from the Meaning Crisis
• Holos Earth Project, "The essence of the holistic perspective and practice is willingness to explore relatedness; to self, to others, and to the world."

My impression is these groups (and systems/complexity groups) find EA thinking "icky" because it is overly:

• linear
• mechanistic 
• reductionist
• deterministic