There's HEAPS of stuff on the resurrection on the web. Anyone can find the best (and worst) sites without too much trouble. Of course, the Internet Infidels is the best place to start.
I will argue that it cannot be doubted that the earliest followers of Jesus had some kind of experience following their leader's death. This experience led them to believe that Jesus was alive again.
The Apostle Paul's Writings
Paul's first letter to the church at Corinth is the earliest document which mentions the resurrection. Here it is:
Some points:
(1) nowhere in the skeptical or atheistic literature have I seen anyone question that Paul wrote this letter in about AD 50-55. I'll take that as a given.
(2) Paul is a first-hand witness to the resurrected Jesus. This is not hearsay. Paul mentions his conversion again in his letter to the churches in Galatia:
Paul mentions his story in passing - the Galatians already knew the details (1:13) - you can read Galatians to find out why Paul is retelling the tale. For the moment we'll look at Paul's conversion.
(3) Galatians was written in either AD 49 or 56. The arguments for these dates are well known and easily researched. After Paul was converted, he went to Arabia and Damascus for 3 years (1:17-18). Then he went to Jerusalem, where he met Peter and James, the leaders of the church there. Then he went to Syria and Cilicia (that is, his home) for 14 years. Sometime before AD 55 he went to Corinth (1 Cor 15:1). So the very latest that Paul could have been converted was 17 years before his first trip to Corinth, and probably earlier than that. Paul was thus converted before AD 37. Jesus died sometime between AD 30 and 33, so there is at most a 7 year delay between Jesus dying and Paul's conversion, and at most 10 years between Jesus' death and Paul talking to Peter and James in Jerusalem. I don't think that its too far-fetched to assume that they shared their stories. Note also that Paul and Peter have some major disagreements (see Galatians 1-2), but never on the resurrection. It is taken as a given, right from the beginning.
(4) Paul distinguishes his own experiences from the others: "last of all he appeared to me also, as to one abnormally born". It is uncertain what Paul means by this. Evidently his readers understood what Paul meant, since he certainly related his story to them while he was in Corinth. Possibly it merely alludes to the fact that Paul's experience happened a good deal later than the others - "abnormally" may also be translated "untimely".
(5) What exactly did Paul experience? Unfortunately he doesn't give us any details, although it is obvious that his readers knew the story - he writes to the Galatians: "you have heard..." and to the Corinthians: "I want to remind you...". Clearly his story was well known. Paul was so widely travelled that most the Christians throughout the Mediterranian would have been familiar with it. We possess a version of the story, as it was eventually received by the author of Acts, in Acts 9, 22 and 26, which may or may not be an accurate recordings of the actual events - I'm prepared to believe that something like this was what happened.
(6) Although Paul's testimony about Peter and James does constitute second-hand evidence, we can be confident about making some conclusions. 1 Corinthians 15:3b-7 was quite probably an early creedal statement. So say the liberal and skeptical scholars. If so, we possess two sources for the conversion of Peter and James - Paul is not simply relating what Peter told him when they met, but citing a creed which expressed the accepted story of Peter and James, which Paul evidently agreed with, having talked personally with Peter and James. James was Jesus' brother (Galatians 1:19), who was not one of the Twelve, and plays no part in the gospel accounts of Jesus' life, other than that of a brother who rejected Jesus. James went on to become the leader of the church in Jerusalem and was martyred in about AD 61. This is related in Josephus' work Jewish Antiquities, section 20.9.1, which is not disputed for authenticity:
Note that some have doubted the martyrdom of the apostles ( here, here and here). It is true that many of the stories we possess are legendary, so we will confine the discussion to those who we have good evidence for - James and Paul. Both had experiences which must have been quite life transforming: they both had major turn-arounds in thinking, from unlikely backgrounds, and both died for those beliefs. James was Jesus' brother. He must have know Jesus when they were both children and thus been highly unlikely to think he was anything like the Son of God. He absence from the pre-resurrection stories seems to confirm this. What happened to change his mind?
The final end of Paul is a little more difficult to nail down with certainty. All the traditions claim that he was beheaded in Rome - the standard mode of execution for a Roman citizen. There is no reason to doubt the truth of this tradition, although it is uncertain exactly when Paul died. Unfortunately the book of Acts finishes with Paul under house arrest and awaiting trial in Rome. Possibly he was released and made his intended journey to Spain before returning a final time to Rome where he was executed, but this is speculation.
Paul records some of his trials in his second letter to the church in Corinth, in which he felt compelled to reply to some preachers who were preaching "a different gospel from the one you accepted" by detailing his own commitment:
Several of these events are related in the book of Acts. There can be little doubt over Paul's amazing commitment to Jesus, without needing to know with high certainty what his final fate was.
Peter presents more of a problem. I guess it is possible that he was unstable after Jesus' death and had some hallucination or whatever. Although I think this unlikely, I won't persue Peter's testimony any further.
(7) Some have suggested that the apostles were liars, using the resurrection story to extort money. This does not explain Paul's conversion. In 1 Cor. 9 Paul mentions that some of the apostles "receive their living from the gospel". If they were abusing that right then Paul would have had ample opportunity to say so here. But the main argument in this direction comes from Acts 5, where Ananias and Sapphira are famously struck dead (presumably by God) for not sharing their money. It seems strange that the skeptic would accept this story as being very early, while rejecting virtually everything else as later legend, apparently including the verses immediately preceeding this story: "There were no needy persons among them. For from time to time those who owned lands or houses sold them, brought the money from the sales and put it at the apostles' feet, and it was distributed to anyone as he had need." (Acts 4:34-35).
So, there is strong evidence that both Paul and James had life-changing experiences which caused them to totally review their opinion of Jesus. Both came from unlikely backgrounds and both persisted with their new beliefs in the face of persecution. Note that I have not attempted to prove the empty tomb, nor the bodily resurrection of Jesus.
2. The crucifixion
By the time of Paul, Jesus was being spoken of in extremely high terms. In Paul's letter to the church at Philippi he quotes another church credal statement:
Paul begins his letter to the Roman church like this:
In fact, all the New Testament documents have this high view of Jesus. There is no sign of Jesus ever being seen as merely a man. This fact presents the skeptic with a problem: not enough time has elapsed between Jesus' death and the existence of such beliefs in order for these beliefs to have developed via "natural" myth-developing processes. The skeptics thus often launch an attack on the reality of even the most basic "facts" of Jesus' life, and assert that nothing about Jesus can be proved beyond reasonable doubt. Jesus could have been a semi-mythical figure who may have lived several centuries before the Christ-myth finally took solid shape in New Testament times (see here for a typical example of such speculations).
The primary problem with such a scheme is that there is not one shred of evidence for it. Nowhere is there any mention of anyone named Jesus or Christ (as a proper name) prior to Paul's writings. There is no evidence for the evolution of a movement which eventually became the early church.
3. The Gospel Writings
As has been pointed out many times, the gospel accounts of the resurrection do not constitute good enough evidence to prove the resurrection beyond reasonable doubt. The major problems are:
(1) it is uncertain when the gospels were written.
(2) the gospels are not first-hand evidence.
(3) the resurrection accounts seem to "improve" with age and gain a legendary character.
(4) the accounts contradict each other.
I would not use the gospels in attempting to "prove" the resurrection. One can conclude that belief in Jesus' bodily resurrection was in existence by about AD 70. Very little else can be asserted with confidence. However, it must be stressed that the problems stated above do not disprove the resurrection. They will no doubt cause problems for doctrines of inerrancy, but not for the historicity of the resurrection.
4. Some links
The most reasonable writings which I've been able to find on this topic are by Jeff Lowder, from the Internet Infidels. His essay is excellent. As Jeff points out, one's opinion of the resurrection is largely determined by one's belief (or non-belief) in God and not by a study of the historical evidence.
The Infidels have a small site devoted to discussing the resurrection. Wunder's piece deserve's serious consideration. Robert Price is perhaps worth reading, although he seems overly keen to be both provocative and intellectual (check out the jargon!), which undermines the value of the pieces.
For those who like the idea that the resurrection is a re-working of the common ancient world saviour-god myth, please check here.
Reasonable pro-resurrection sites:
Justin Taylor