One of my readers asked a good question about the "forbidden gospels", so here are some quick, not completely thought-out comments on this subject:

1) They're technically called "non-canonical." That is, they're not part of the canonical Bible which includes 27 New Testament books including the four canonical gospels: Matthew, Mark, Luke, and John.

2) There are reasons why the non-canonical gospels are clearly false or minimally have false elements in them. These reasons can be very confusing to someone who doesn't understand the context of the time, of the writers, and of the books' purposes for existing. The reasons are hard to explain to beginners (and I'm a beginner myself here), but essentially you have to realize two very important facts:
A) Oral tradition was more important than written tradition at the time and treated differently than you or I might expect. Specifically, there wasn't a huge desire that things be completely accurate in writing.
B) There were several "Christian" groups in the first/second century, and each had their own agendas (more-or-less). As an easy example, some wanted to show that Jesus was either only a man, only divine, possessed by a spirit, 50% man /50% divine, or 100% man / 100% divine.
As a specific example of one group (or better stated, several groups), there were people called Gnostics. Many Gnostics believed that they had special "gnosis" (thus their name) or "knowledge" that was passed to them by Jesus and would help them escape the material/evil world. This "gnosis" was to be kept secret, unlike our current Christian idea of passing on the gospel. They often worshipped in Christian congregations with other non-Gnostics (but would not let these other Christians know they were Gnostic). Some Gnostics believed that Yahweh (the Jewish God of the Old Testament that we now call "The Father" or "The Creator") was essentially an evil god who created the material world and that all material is therefore evil. They basically believed the Christ took control of Jesus' body (to the point that they literally believed jesus was more or less a robot for the christ) so that Jesus could pass on the special gnosis required to escape the material world to get to the spiritual realm. They believed the Christ was a spiritual being who basically possessed Jesus then left him to die on the cross.

I am not kidding or exaggerating here. I hope this provides some understanding as to why this stuff is so complex, because the Gnostics weren't the only "other" Christian group. If you want examples of Gnosticism, they are fairly easy to see in both the non-canonical gospels of Thomas and Peter, for example. At the same time, I strongly recommend you don't read this stuff unless you fully understand who wrote them and why, because as I said, the context and purposes for their existence can be very confusing.

3) A more modern example is easy to point to with the Da Vinci Code. I did read this book to see what the hoopla was all about. Again, I don't recommend reading it or any of the above books if you don't have a good grasp on why they were written. For example: Da Vinci Code was written and made into a movie--why? To make money. The Gospel of Thomas was written --why? To pass forth secret "gnosis" to escape the material world.
There are many reasons to take Da Vinci as "gospel," when in fact it's just fiction. The most obvious thought I have about it is that the book itself says that Da Vinci basically hated the Church and lived in the 14-17th Century. So, are we to be surprised that he tried to bite his thumb at the Church with his little practical jokes? I say not. Further, are we to throw away literally centuries worth of tradition because of these jokes? I say not. Are we to say that his version of the Last Supper supercedes what was written in the first or second century (ie. much, much sooner to Jesus' time) by second or third generation Christians (with the apostles being the "first generation")? Again, I say this defies any sort of logic.

4) All of the non-canonical gospels that I've read or looked into were written later than the canonical gospels.

5) There are a ton of theories on how the gospels derived from each other, but the one I studied in my New Testament class (and the one I right-or-wrong currently subscribe to) is essentially:

a) All four canonical gospels were anonymous. That is, we don't know if the authors were really named Matthew, Mark, Luke, and John for sure, but we use those names for the authors by tradition and because there are reasons to believe they may be correct. One reason we don't know for sure is--again--largely because the written tradition in the first century and second century was very, very different from now.
b) Mark was written first.
c) Somewhere before the rest of the canonical gospels were written, three other "sources" came about. they have not ever been "found" in pure form, but there are reasons to believe they existed. they are called:
1. "Q" from the German word "quelle" which in English means "source." "Q" is definitely believed to have existed, and I've even read of it in Catholic bibles. Q is believed to have been a source or book of only Jesus' sayings (similar to the non-canonical Gospel of Thomas, but much earlier and without all of the Gnostic undertones. In other words, Q is seemingly more likely to have been authentic sayings of Jesus.
2. "M" as in a source that fed into Matthew. Some people believe that M may have just been oral in nature and not written.
3. "L" as in a source that fed into Luke. Again, some people believe that L may have just been oral in nature and not written.
d) Matthew and Luke wrote their versions of the gospel after Mark but before John. Both of them used Mark's version and "Q." (In fact, the reason some experts believe in the existence of Q is that there are matching passages in both Matthew and Luke with literally the same exact wording. Many experts believed Matthew and Luke basically cut/paste Q into their gospels.) In addition, Luke used "L" and Matthew used "M."
e) John was written more-or-less separately from the other three "Synoptic" gospels. In other words, although John was written after Mark, Matthew, and Luke, there is no solid evidence John used the other three gospels. Further, 90% of what's in John isn't in Maark, Matthew, or Luke.
f) Just like the various groups of Christians focused on making different points theologically, each of the four canoncial gospels have their own focuses as well. (I'll save that for another time though.)

Hope that helps. I hope to clean this up at some point (when I have some time to do a more thorough job).