Some of this information might be obvious but to be honest I never really considered paying any attention to these sorts of organizations until my parents joined one. The entire process is not only fun, but it seems as though it can have lots of professional impact on one's life as well. I do not live in the USA but if I did, i would definitely look to join one of these things.
I am referring to the Benevolent and Protective Order of Elks, more commonly referred to as "The Elks' Lodge" or simply "The Elks."
I am not sure how many lodges they have accross the USA but there are over a million members and it seems as though any town of consequence has a lodge. I have only ever been to 2 lodges, and both times were with other members (because you can't come in unless escorted by a member) and it was always a very welcoming environment. The lodges do engage in a lot of charitable activities as well but one of the main aspects of the lodge that I really enjoy is the social side of it.
I suspect that each Elks' lodge is different but they all seem to have a bar and restaurant and they are always very inexpensive. They are able to make drinks cheaper because of the fact that it is subsidized by membership fees and also there are tax benefits to being a private club. It is practically unheard of to get a beer for $2 anywhere in the States but at the Elks' it is easy.
Also, people can bring their own bottles of booze in and keep it there. I think this varies from state to state but the one near where I am saves money by only having an alcohol license for beer and wine, so if you want spirits, bring your own and pay for the mixer. I don't know how it works but it does.
There are a couple of other benefits of being a member of the Elks other than booze, although that is a good one.
There are wonderful opportunities for networking here. The people that are members of the Elks come from all walks of life and some are quite successful, others not so much. The point being that if you need some help or want to expand your business opportunities, the members of the Elks, nationwide, through a sense of fraternal obligation, are extremely likely to help you. As someone with a high level of education that hasn't seen much career benefit from it, I can attest the the essential power of networking and nepotism and the Elks lodge has this in spades.
Another benefit is that if you are traveling the country with a motorhome or even a pull behind motorhome (referred to as a trailer or "fifth wheel") and are a member of the Elks, you can park in the lot and hook up to water and electric, use the wifi and showers at the lodge for free. This is a wonderful aspect of the lodge and a great way to meet some people along the way. Everyone in these places loves a traveler, and as strange as it might sound, they are kind of obligated to be nice to you since you are in the same "club."
a very common sight in the Elks parking lot
I love the Elks, and I would imagine MOOSE, Rotary, and Masons are similarly great. If I lived in the states i would definitely join. However, this bring about the only downside: You can't just join because you want to. You have to be invited by a member and the existing lodge leaders must approve your membership. I have no idea what does into this process, but well, i have never heard of anyone being denied.