Gumby, there are some very reliable sources to get answers to your questions here on the internet. Or also there are plenty of books you can read. (None of which the publisher is the Watchtower - since we know their record for being intellectually dishonest I don't recommend their book "All Scripture Is Inspired By God")
For starters, it was not the intention of the bible writers to have a collection of books. Paul, for instance wrote letters to congregations during his lifetime about things he had first ORALLY taught them.
None of his letters were intended to be catechisms, containing EVERY TEACHING of the Christian Church. Most of the Christian Traditions were taught orally and only when something went wrong was a letter necessary. Paul, In my opinion, probably never imagined his letters would be fought over 2000 years later by 10,000 sects all claiming to be the "original" Christians.
Regardless of the claims of many, there obviously was an organization of men who first decided it was necessary to collect and preserve and then proceeded to collect and preserve the books we now include in our Bible. These same men decided what the criteria would be for a book to be considered "inspired" and thus warrant its inclusion in the collection.
The Canon wasn't decided in a vaccum. It took hundreds of years before it was finally AUTHORITATIVELY established.
So maybe your question should be, "Who had the authority to decide the canon?"
In fact, that's a good question for all "Bible believers" to ask themselves because obviously God didn't come down from heaven and throw the books at us, did he?
Someone already mentioned Irenaeus and Eusebius. Isn't it interesting that before the canon of the Bible was established, the doctrines of the Trinity, Hellfire, Immortality, Eucharist etc. were already in place. I mean Christians didn't even agree on which books were inspired but they already had a universal creed.
That's because the Bible was one of many Traditions of the Christian Church which evolved. First came the oral Tradition and out of it came the Written Tradition.
So when JWs or fundies say the Catholic Church practices "traditions of men" they are forgetting that the establishment of the Bible is one of those Traditions they are calling a "tradition of men."
If a person is interested in historical facts, well it is undisputed that the Bible is a product of the Catholic Church. Even if one wants to say the Bible came from God, they still have to admit that God used the Catholic Church as his "channel" or "organization" to give His Word.
The Catholic Church is responsible for preserving the books, as Amazing pointed out, they still have the documents at the Vatican. They are responsible for deciding which books belong in the canon. They are responsible for copying the books throughout the centuries. Throughout the centuries when most people were illiterate, they were responsible for teaching what was in the books to the people.
In the middle centuries the cost to own a bible was equal to the cost of buying a house. So, needless to say, most people didn't have a bible of their own. But the scriptures were read every day in Mass. And there were bibles chained to Churches (because of their value) in order for people to have access to them.
That is why the Catholic Church claims responsibility for interpreting the books they themselves canonized. The Catholic Church has always maintained the goal of preserving the original Christian teachings. Do you think they would have included in the canon of scripture teachings which contradict what they themselves believed?
Many people who detest the Catholic Church accept the traditional Canon of the New Testament. By doing so, they necessarily acknowledged the authority of the Catholic Church.
And yet at the same time, they follow the tradition of Luther and discard 7 of the books which were part of the original canon. Why they don't discard James and Revelation I don't understand since Luther also wanted to do away with those books. If he had had his way, we wouldn't have Revelation and thus, probably no apocalyptic sects like the JWs, who claim to have the correct interpretation for that book.
If you want more info on the canon, for starters you can go to this link and then pick up from there.
http://ic.net/~erasmus/ERASMUS3.HTM#CANON OF THE BIBLE AND THE APOCRYPHA