"I ask, sir, what is the militia? ...
... It is the whole people except for a few public officials. "
-- George Mason
And you can find more pearls of wisdom from this man who gave us the Bill of Rights here:
http://www.brainyquote.com/quotes/authors/g/george_mason.html
As for what a militia is today, it is still what the Founders intended it to be. It only seems "odd" for two reasons:
1. There are a lot of groups that do not fall under the definition of militia as the Founder prescribed, but call themselves militias. The term itself is generic. Patriots banding together to fight for their freedom is a militia, as were the hurricane Katrina survivors who got together under arms and brough order back to their neigborhoods. Sadly there are a lot of morons out there who call themselves militia, and many criminals operating within identity or radical groups, when caught by the feds, are instructed to use the M word more for propaganda purposes. Even the media said that Timothy McVeigh was in a militia when in fact he was not. For a time the ADL pushed that line until a lawsuit started brewing over it.
2. People are so fearful of not only the M word, but of guns too. Therefore while the militia comprises the people, so few of the people actually train in that context it appears rather extreme. Add to that the work of the NRA pushing the gun are for hunting and personal defense angle for so long that the mere implication that the 2nd Amendment was intended to keep tyranny at bay is enough to get most of the "golfers with guns" nervous.
As for "joining" a militia, the closed recruitment thing is falling to the wayside as well. Failing to recognize the militia for what it is, according to what the founders thought it should be, opens a door to various problems. That of which most prominent are those who end up calling themselves "general" and start strutting around in a uniform all because they got their two cousins to agree to the idea.
So over the last 10 years there is a slow migration toward the concept that the militia already exists in the populace, and those "militia operators" are becoming more of a training cadre and offering time and effort to the cause of training the populace in the use of armaments, along with other ideas and related topics (survival, rally points, self reliance, etc).
Funny that you mentioned survivalists. Survivalists and militia are usually considered the same group and many times the equipment and ideas are the same but survivalists are more interested in getting away and hiding out in the hills and waiting out the trouble while militia are not going anywere, or only long enough to escape immediate danger. And considering the changing times and the growing police state, hiding out in some cabin on a mountain only means the tyrants minions have all the time in the world to make you their project. From tyranny, esecially with the control grid being put in place, there is nowhere one can hide.
As for what to expect from going to a militia meeting or something like that, I would be wary of anyone who outright and openly calls for the making of machine guns and bombs or the killing of people who have yet to give good reason for it (indeed that is a sore subject considering the level of treason going on these days). Since the mid-1990s the feds have made it their MO to join up with militia groups and then bring illegal stuff and push for crimes, thereby setting up everyone involved. Then the media gets another hit piece calling 2 guns an "arsenal" and the club house a "compound". I would agree that the NFA is BS and there are a lot of treasonous types needing tar and feathers but he who openly tries to get something done like that or make these items is usually an informant on a fishing expedition. In all setup cases I know of the feds try to make informants out of their targets.
Again, if you have guys strutting around calling themselves "General" or colonel or something like that, you might be dealing with people not running on all 8 cylinders. Groups that use cronyism and giving themselves or each other rank tend not to be very productive and when all is said and done they do more harm than good.
(but...... I AM NAPOLEON!)
While it is often said that patriotism is the last refuge of the scoundrel, politics is the first. Therefore the militia is plagued with egomaniacs, blowhards, and various other negative nabobs of negativism. I could tell stories all day about this and some of the crap I have seen.
Partly because of that crap, and partly because of the changing landscape of lawfare where there are many pitfalls (like informants) and gotchas (PATRIOT Act, Military Commissions Act, SB1955, etc), the new structure for militia is actually going back to the original old structure of a community based decentralized organization using standing orders, a well regulated set of standards for shooting, and a code of ethics. The days of large centralized groups practicing infantry tactics from 1960s Army manuals are gone. Small units are now encouraged and those looking to be a more active militia operator are encouraged to create their own small unit consisting of friends, family, and close neigbors. There are arguments against this however because decentralization can lead to trouble with mission crossover and fratricide but these issues are in consideration for quite some time now and they are being dealt with. Communications and networking through smaller channels (individual contacts between small groups) are heavily emphasized along with standardization of target selection. Did I mention ethics? I mention ethics again.
I could go on all night about 5th Generation Warfare, 4th generation warfare (of that Bill Lind writes about best), special weapons, etc. But there are others who are better at that. I am mainly too busy leading my troops into Prussia right now but I alerted better men to this thread who will explain things much better than I can.