One of the things that consistently impresses me is community organizations and how much a difference they can make. Lately, I've been doing research on various organizations, and thinking back fondly on my own time at the ones I used to work or volunteer at.
One of the ones that has caught my eye is the Rhizome Collective. The idea is that, like a rhizome, they started small but grew roots that went all over the place. They work mostly in finding more sustainable ways to live, and they've even published books on the subject.
This group is located in Austin, Texas (which I always hear so many nice things about), so sadly, I can't join them because of geography, but if I ever end up there, I'll have to think of swinging by.