On AlabamaAtheist.Org, Blair Scott has up an editorial entitled "Did Jesus Exist?" I'm going to quote some of it (in italics) and give my thoughts:
It is important to note that there is zero evidence for Jesus. All the "Gospels" and other references about Jesus were written after Jesus' death, so none of the authors were first-hand witnesses to the life of Jesus.
The gospels show some pretty clear evidence of having been based on oral tradition which preceded them. Although there is no guarantee that an oral tradition will be accurate, it is important to ask: Is it more plausible to suppose that a real person inspired the legend or not? After all, we see lots of cults who ascribe miraculous powers to their leaders and believe that they are more than human. That could be the case here. As I mentioned to Blair at my local meetup, we also have Josephus, which most scholars accept. I do not accept it for many reasons, one of them being the fact that Josephus probably would not have had nice things to say about Jesus if he had written about him. After all, Josephus was not a Christian and viewed messianic contenders with suspicion.
When you are selling a religion and passing down oral tradition, the stories change. What good is a messiah that cannot resurrect? So the early apologists (which is essentially what the Gospel authors were) added a resurrection to make it fit prophecy. What good is a messiah born in Nazareth that was supposed to be born in Bethlehem according to prophecy? So the authors changed the story to read Bethlehem (note the Gospels disagree on Jesus' birthplace: writers changed it to match the prophecy). This goes on and on...
I agree with all of this completely. However, I think we should keep in mind that since a crucified messiah would not fit the Jewish expectation, this naturally fits the idea that Jesus was just a guy who's story got embellished: After all, if it was complete bull, why have him crucified in the first place?
On the other hand, what if the gospels are "midrash" -- Reinterpretations of Old Testament Scripture? This is what I have argued before, I think it remains plausible (read the link to understand how this pertains to the crucifixion).
I've also learned that the cross was used a symbol to represent the messiah in some ancient Hebrew manuscripts, so having the Savior hung on a crosee might not have been so embarrassing: Indeed, it may have been a dramatic and ironic confirmation of what Jesus was (in the story). [For this info, see Page 62, Rodney Stark, The Rise of Christianity, HarperOne, 1997.]
As a final note, I want to say that I do not think "no evidence outside the gospels" is a good argument for Jesus' nonexistence. Most of the time we do not doubt the word of historical documents, unless they are outlandish or conflict with other knowledge that we have. While that may destroy the Christian's case for the resurrection, it is still completely plausible that there is a man behind the myth.
Now, some may say that you cannot prove a negative. I think this is clearly false. There could definitely be positive arguments against the existence of Jesus (Watch this video and skip to about 1:25).
In conclusion, I am remaining agnostic about the historical Jesus until I find more evidence either for or against him, and I think that Christians and secularists alike should also keep an open mind.