I am very interested in the Freemasonry, and often contemplated becoming a Mason myself sometime in the future. My grandfather is a Mason of a fairly high rank. I don't know all that much about the Masons, but I can answer some basic questions.
The Masons go back to Biblical times. There's even mentions of the Masons in the Bible itself - Masons built King Solomon's palace, and King Solomon is probably a Mason himself.
The Masons went through a evolution recently from a practical, prestigious masonry group into a society that accepts non-Masons. Today it's a secret society that accepts men from all walks of life. Contrary to rumors, you do not have to have family members in the Freemasonry to become one yourself - though it does help sometimes. To join, simply go to a Mason Lodge and get a Petition form where you fill out and submit. They will bring your Petition up in the next meeting and the Masons will decide whether to invite you into the society or not. The meetings are not secret either - you can go in a Lodge and request a minutes for the latest meetings. There are less secrets in the Masonry than you might think.
Many people think the Masonry is for Christians only. That's not true. They're not a religion-based society. They are, however, "deity"- based society, meaning you must believe a god or another to become a member. The reason for this is that upon initiation, you make a promise upon your deity. They believe that if you don't believe in a being such as God, that you have no foundations to set your promises to, that you have no reason to oblige to your promises.
The structure of the Masons break down into three groups, I forget what the lowest group is called, but the middle one is Masters, and the top one is the Masons. At least I think so. The lowest group might be Apprentices, I'm not sure. There are degrees of Masons, ranking up to at least 33rd degree.
That's all that comes to mind right now. Any questions and I'll try to answer. Keep in mind that I'm no expert, and the above is related to me by my grandfather.