Origins of Freemasonry
Starting in the year 1717, the Grand Lodges of Freemasonry can be found in most countries all over the world. The history of Freemasonry dates to well before then of course, probably back before 1390.
Years prior to the formal founding many informal lodges existed but little hard documentation remains to provide a firm date for Freemasonry's beginnings.
Criticism of Freemasonry
Some have criticised Freemasons in the past for being excessively private, with insufficient transparency in their dealings. As a consequence of this many have accused Masons of furthering each others' interests ahead of non-members.
Lodges have recently opened up to the public, with open days, newspaper and magazine interviews etc. all in attempts to assuage the concerns of an over-arching conspiracy. Needless to say this has not reduced the interest from the tin-foil hat brigade.
Becoming a Mason
Masons are recruited by individual lodges from candidates recommended by existing members of that lodge. Prospective Masons must proclaim a belief in a Supreme Being, who may or may not be the Protestant Christian God. Your prospects of being accepted if the Supreme Being you believe in is not the Protestant Christian God vary depending upon whether the lodge is in Norn Iron or not.
The initiation ceremony also varies a little between lodges, but few are believed to involve even half of what has been rumoured over the years; although the wearing of silly aprons is well-documented.
Basically Freemasonry is like the Rotary Club but with even less humour and even more in the way of obscure silly rituals. Membership isn't supposed to improve your chances of promotion, but if you're a passed-over Major, it's worth a go.