I had a brief moment between grading stacks of papers, so I thought I'd make a quick point:
One argument that William Lane Craig uses as a part of his case for Jesus' resurrection can be summarized as follows:
The origin of belief in Jesus' resurrection must have been derived from either Christian sources, Jewish sources, or from experiencing Jesus as risen from the dead. But the belief couldn't have been derived from Christian sources, for Christianity didn't arise until after (or simultaneous with) the belief that he had risen from the dead. Nor could it have been derived from Jewish sources, since the Jews had no concept of a single individual being resurrected prior to the general resurrection at the end of time. Therefore, it must have arisen from experiences that they took to be of a resurrected Jesus.
The argument can be expressed a bit more carefully as follows:
1. If belief in Jesus' resurrection was due to something other than experiences as of Jesus risen from the dead, then the belief was derived from either Christian influences or Jewish influences.
2. If it was derived from Christian influences, then Christianity existed prior to itself.
3. Christianity didn't exist prior to itself.
4. Therefore, it wasn't derived from Christian influences. (From 2 and 3)
5. If it was derived from Jewish influences, then the idea of a single individual rising from the dead before the end of time was extant in Jewish belief prior to Christianity.
6. The idea of a single individual rising from the dead before the end of time was not extant in Jewish belief prior to Christianity.
7. Therefore, it wasn't derived from Jewish sources. (From 5 and 6)
8. Therefore, the belief wasn't derived from either Christian influences or Jewish influences (From 4 and 7)
9. Therefore, belief in Jesus resurrection was not due to something other than experiences as of Jesus risen from the dead (From 1 and 8)
As you can see, this argument is deductively valid. However, it looks to be unsound, as at least one of its premises looks to be false, viz., premise (5). For as a number of NT critics have pointed out, and as is fairly clear from the writings of the NT itself, the earliest Christians believed that Jesus' putative resurrection was (to use Paul's terminology) the "first fruits" of the general resurrection of the dead at the end of time. This is an agricultural metaphor. When farmers reaped and ate the first fruits of the harvest, they would then reap the full harvest the very next day -- the "general" harvest was "imminent", as it was "inaugurated" with the reaping of the first-fruits. Similarly, the earliest Christians believed that the final judgement and the general resurrection were imminent, given their belief that Jesus' resurrection was itself the inaugurating event of the general resurrection and the end of all things. Thus, contrary to what Craig says on this matter, there is a continuity between the beliefs of the early Christians and the beliefs of many Jews of his time: Jesus' resurrection was fundamentally construed in these eschatological terms. And of course, as Craig acknowledges, the idea of a general resurrection at the end of time was a common Jewish belief at the time. Thus, premise (5) is false, and the argument is unsound.
In short, the answer to Craig's question, "Where did the Christians get the idea of a single resurrection prior to the end of time?" is: "They didn't. They construed Jesus' putative resurrection as the inauguration of the general resurrection at the end of time, which of course was a popular, traditional Jewish idea in Jesus' day. That's why Paul called Jesus 'the first-fruits' of the resurrection, and partially why Paul and the early church in general believed that the end of time was imminent.", 
 Which conforms nicely with the hypothesis/research program, held my the majority of NT scholars for the last century, that Jesus was fundamentally an eschatological prophet. See my earlier post for a brief sketch of some of the other evidence in support of this hypothesis.
 Question: But where did the earliest Christians get the idea of an imminent eschaton to begin with? Answer: From Jesus' fundamental message: "Repent, for the kingdom of heaven is at hand!" For a nice introduction to the research program of Jesus as an eschatological prophet, see Bart Erhman's Jesus: Apocalyptic Prophet of the New Millenium (Oxford, 1999). For more details, see Dale Allison's Jesus of Nazareth: Millenarian Prophet (Fortress, 1998).
 Others have critiqued premise (6), on the grounds that in the NT itself -- viz., Matthew 14:1-2 -- Herod believes that Jesus is John the Baptist risen from the dead(!):
"1At that time Herod the tetrarch heard the reports about Jesus, 2and he said to his attendants, "This is John the Baptist; he has risen from the dead! That is why miraculous powers are at work in him."
But if so, then if the passage is historically accurate, then it's not true that the idea of a single individual rising from the dead before the end of time was not extant in Jewish belief prior to Christianity. In other words, premise (6) is false.