I'm active in Toastmasters and martial arts (mostly the community of my specify school). Overall Toastmasters seems pretty effective at its stated goals of improving public speaking and leadership skills. Its also fun (at least for me). Additionally, both force me to actually interact with other people, which is nice and not something that the rest of my live provides.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.