Many such complaints are not a coordination problem, but rather a cheap-talk problem. Lots of people complain, but aren't willing to actually make sacrifices to change things.

Coordination of letter-writing, voting, marching, etc. happens pretty regularly.

It's certainly technically possible, though it needs some thought about how causes and actions get contributed and vetted.

It should probably have a geographical component so people can coordinate on local issues.

It could also use a way for people to at least sign in and say they did the action they committed to. Asking for them to prove they did the action is probably too much to ask, though in the case of writing letters, they could post the letter. They could post pictures of themselves showing up at demonstrations.

Getting people to know about it and use it is a coordination problem in itself. What it' would be like if it's non-partisan would be interesting, and it would also be interesting if it's set up to be partisan.

I suspect people don't have a clear idea of how many people they want to make a commitment before they'll do something, but maybe thinking about the question is useful in itself.

If it catches on, it will need to be financed.

At least kinda along these lines: Thunderclap, a thing that arranges for many people to send out social media messages simultaneously conditional on enough people declaring willingness to do so.

(Note 1: using this means giving the people who run it more access to your social media accounts than you may be comfortable with. Note 2: I haven't used it myself and have no first-hand knowledge of how well it works or how suitable it is for political activism.)

I am fascinated by the example of Free State Project. Short version: Americans sharing the libertarian political view are coordinating to move to the same state, so together they can have greater impact on local politics.

This is a difficult problem, because talk is cheap, but moving to a different state is expensive. (Not only just the costs of moving per se, but you will need a new job, you may lose your social network, etc.) And unless many people do it at once, the project fails (but those who moved still pay the cost). Different people will have different opinions on what the best state is. Et cetera. Also, many things can go wrong, for example the people living in the state may be worried about you and try to stop the project, or a competing political party (with much more members and media power) could somehow coordinate against you, etc.

If you would ask me before the project started, I would say it is hopeless, and maybe use it as a textbook example of something. Even at the beginning it didn't seem very hopeful. The project has started in 2001, and hasn't finished yet.

So, what did they do?

First, they created their own website. (This already requires some coordination, otherwise it can easily happen that no one would create the website, or there would be multiple competing websites each proposing a different solution and different method for coordination.) I believe this is important, because if you use someone else's website, you are at their mercy. If the website belongs to a private company, and the people in the company disagree with your goals, they can easily sabotage your whole project, and there is nothing you can do about it. People are often not aware of this, because we take some parts of internet for granted. But you can easily in the middle of your project get a message that e.g. "your project is against our terms of service" and have your data removed; and the terms of services may change from one day to another. Even more dangerous would be the silent censorship, such as shadowbanning on Reddit, or removing inconvenient hashtags on Twitter.

Then they had a debate and voted on the state they are going to move to.

Then they published a pledge for people to sign, saying that they will move to the selected state within 5 years after 20000 people have signed the pledge. Even this contains some risk, because many people can sign the pledge and then not move. I would rather think about the pledge as the upper bound -- if you cannot even find N people who sign the online pledge, you are probably not going to find N/2 people who will really do it; and if that is the case, you want to know.

Now, fifteen years later, they are at 95% of the required 20000 people. There is still a risk that when they reach 100%, they will find that many people have changed their minds, or that many signatures are fake. On the other hand, anyone who signed the pledge was free to move there sooner, some already did, and their numbers are published too, so people who say "I don't really care about how many people signed something online, but I am interested in how many people already did it" also have data.

tl;dr:

• have your own website
• publish a pledge "I promise to do this if N people promise the same thing"
• keep updating the number of people who signed the pledge and the number of people who already did it
• be very patient; it could take years