I usually start with The Big List of Protests, where a lot of stuff gets cross-posted. Political revolution gets the 50501 protests and some other stuff (note that the site has had connectivity issues when but protests are upcoming and we in the outside aren't sure if that's bandwidth issues, hardware/software limitations, or sabotage. If you see an upcoming protest that looks possible, screenshot it just in case you can't look it up later.] Indivisible runs their own calendar (they have connections with the Democrats, so I wouldn't use my real contact info with them unless you want you start getting mailers and begging letters), and there's also No Voice Unheard.

50501 on reddit recently had some kind of moderator drama (idk i heard about it in passing). The original moderators have a new sub at /r/50501movement, but /r/50501 is still active and I'm not sure how many people know or care about the difference. Depending on how active it is, you may be better off using your state or regional 50501 subreddit anyway.

If you can't make a protest, or don't want to, you can start with Five Calls, which lists current events or upcoming votes to talk to your Congresscritters about. They suggest choosing one topic each day and making one set of calls every day, but any calls you can make are important. Apparently they're semi-ignoring emails and letters, as so many of them can be brigaded, but they're still paying attention to phone calls - possibly because the constant ringing is annoying. [If you end up in voicemail, try calling one of the local state offices for your Congresscritter.] If they hold one that you can get to, to go a town hall so they can see lots of angry faces.

I will note that one reason the Republicans have had so much influence over their Congresscritters is that, apparently in the past, they got 4 phone calls from Republicans for every one phone call from a Democrat. I'm not sure where the math currently stands. If you have any connection with the Congresscritter, mention that: "I worked on/volunteered for/donated to their campaign" (even if it was decades ago), etc. If not, try for some other connection: "I've voted for your party my entire life", "I live in [member's] home town/office town", "They were wonderful and helped me with this problem years ago", whatever you can think of.

If you are calling, this one's important: if they do something you approve of, call or write and let them know that as well! No one's going to like getting yelled at all the time, and we can give them both positive and negative reinforcement. So if Cory Booker or Hakeem Jeffries or anytime else does something noticable you approve of (the sit-in, the filibuster, whatever) call and thank them, even if they're not your Congresscritter, then call your Congresscritter, tell them how impressed you were with the other guy's actions, and ask them to support your cause-of-the-day.

There are a lot more resources out there, and many more things you can do to help, but those are the ones I'd start with.

This organization seems to be doing a lot of heavy lifting for the protest.

https://www.fiftyfifty.one/

There are several communities on Lemmy that mirror information from reddit about it if you search 50501 on here.

I mean you have to be a bit plugged in. Im not sure if news communities will take down one talking ahead of time but its not really news till it happens. !50501@piefed.social is the place to go when your part of the federation.