One Palestinian journalist said that "the situation in the north is horrific and very dangerous" and implored people to "please share what's happening."
Whichever ones are active at any local protests or actions. If none are, then a socialist organization that does not mince words about support for the resistance. If you are in college there are anti-imperialist orgs organized specifically by and for college students.
I would be more specific but it's more important to find an active org with a good line on Palestine (e.g. one that opposes Harris, supports fighting against Israel) than it is to join one specific national org.