I've been a long-time member of Amnesty International, the world's biggest human rights organization.
They have "sections" (groups) in almost all parts of the world, so if you have a bit of spare time and are keen getting to know some smart and interesting people, search for a local group, there might be several in your own town! (E.g., most Universities have their own group, often on top of a local group of a city.) Talk to me about it if you'd like to.
I am also a member of (German) non-profit foundation that publishes books (by professional authors as well human rights experts etc.) about human rights, Edition Kettenbruch.
Although we only published German books so far, feel free approaching me if you have ideas for future books, know interested authors, or would like to offer your services.