One of the biggest movers and shakers in the early Christian church was Paul of Tarsus, originally known as Saul and who had his vision of the road to Damascus where Jesus appeared to him and asked him why he was persecuting his people. This was the first time Paul had seen Jesus, since he wasn't one of the original twelve disciples and Jesus, at this point, had already been crucified.
Following his apostasy (interestingly, a word we get via a different route from the similar “apostle”, but we'll get around to word meanings in a bit) Paul spent the best part of the next 30 years preaching to the Gentiles with at least two visits to Jerusalem before he ended up in Rome, which he may or may not have claimed to be a citizen of.
From the fact that Christianity's base is still in Rome, you may get the feeling that Paul had a lot to do with founding it. Some even refer to Pauline Christianity to differentiate the origin of what is essentially modern Christianity from what Jesus himself was trying to achieve.
Of course, Catholicism today doesn't deny Paul had a role in its creation and he is now a Saint. But the official line is he was still following the road Jesus had started.
There are, of course, dissenting views - mainly outside the Churches, Synagogues and Mosques. One of these is that Jesus didn't have any intention of starting a new religion, but instead intended to free the Jews from Roman occupation. The Jews were/are expecting a Messiah (from the Hebrew: “the anointed one” in reference to the oiling of the priests, prophets and kings of the Jews) to come along at some point to sort things out and they have a number of requirements he needs to meet, one of which is that he was of the line of David (the lad with the sling and the Goliath killing).
Jesus Christ (Christ, from the Greek “Khristos”: “the annointed one” 
actually qualified doubly in this since both Mary and Joseph were descendants of David - though, obviously, under the Christian interpretation, Joseph wasn't the daddy; but then, that doesn't matter since under Judaism, the line is traced through the mother anyway. I read once somewhere that Mary was also descended from the priestly line, so Jesus was supposedly both priest and king of the Jews (Mary, of course, being a chick, not eligible as ruler).
There were other prophecies around the Messiah, including his entry into Jerusalem on the back of an ass, which Jesus went out his way to fulfil. He also stated that he was here to return the Jews to Judaism, which had rather been lost since the Romans had installed their puppet leaders in Jerusalem. Matthew 5:17-18 'Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.'
Then there's the bit where Pilate interrogates Jesus. There's been some fiddling with this over the years, because, essentially, it was a huge clue as to what Jesus was up to and contrary to what the Catholic church wanted people to believe. In the King James version of the bible - from the 17th century - the discussion goes as follows:
And Jesus stood before the governor: and the governor asked him, saying, Art thou the King of the Jews? And Jesus said unto him, Thou sayest.
So that's a no. Or is it. Some modern versions run the translation of his reply as “It is as you say” or even “Yes, it is as you say”. Equally, some still translate it with a negative swing. In “The Message” bible - published most recently in 2002 - the reply is “if you say so”. Regardless, Pilate sticks a sign saying “King of the Jews” on Jesus before sending him off to be crucified.
So with dodgy translations, we come back around to the virgin birth of Jesus. The original versions of the bible use the Hebrew word `almah to describe Mary. This can be translated as “virgin” or alternatively as “young woman”, in the same way that the English word “maiden” can (witness “maidenhead” meaning the hymen). Greek translations use parthenos. which, if you've ever read up on Aphids, you may recognise as having a large virginity meaning from parthenogenesis. However, like maiden and `almah it also has alternative meanings, including “unmarried women who aren't virgins” (emphasis mine). Further, in other places in the Bible where parthenos is used, the virginity of the woman in question is specified - an oddity that, in English, would be like saying “the virgin, who was a virgin”.
Personally, I think it stems from a desire in language to say that all young women are chaste. Virginity in a woman is heavily desired by men - witness Mizuage, the sale of a Geisha's virginity - especially in a wife, and another meaning of `almah is said to