The following is a paper of mine I wrote for one of my classes. I found the topic to be especially interesting, so I thought I would share some musings.
There are a plethora of passages about Jesus from historical antiquity. What may surprise some people is the vastness of non-Christian (i.e. Jewish and pagan) authors who mentioned Jesus. Although not every text is equally well-attested, a number of facts the NT claims concerning Jesus are confirmed by these other sources. With that said, the NT contains the primary sources of our knowledge about the life of Jesus. These additional quotations may be used in our subsequent attempts supplement what we know, or else confirm what the NT already says. We might begin with what some early Jewish writers had to say.
A quotation from the Tannaitic period of the formation of the Talmud (ca. AD 70 to 200) has this to say:
“On the eve of the Passover Yeshu [Jesus] was hanged. For forty days before the execution took place, a herald went forth and cried, 'He is going forth to be stoned because he has practiced sorcery and enticed Israel to apostasy. Any one who can say anything in his favor, let him come forward and plead on his behalf.' But since nothing was brought forward in his favour he was hanged on the eve of the Passover.” 
“Yeshu” is the equivalent of both “Jesus” and “Joshua.” While one may be caught a bit off guard by the mentioning of death by “hanging,” the NT uses this term to refer to crucifixion, as well (Gal. 3:13; Luke 23:39).  From this text, we also find confirmed the facts of Jesus' trial, the wonders he worked (which these particular Jews considered “sorcery,” as opposed to acts of God), his following, and the disciples' desertion of him. For, even though Jesus had allegedly brought Israel to apostasy, none of the “apostates” were willing to stand by him.
The Toledoth Jesu is a controversial text that was compiled after the fifth century AD. As Habermas explains the text as follows:
“It relates that his disciples planned to steal his body. However, a gardener named Juda discovered their plans and dig a new grave in his garden. Then he removed Jesus' body from Joseph's tomb and placed it in his own newly dug grave. The disciples came to the original tomb, found Jesus' body gone and proclaimed him risen. The Jewish leaders also proceeded to Joseph's tomb and found it empty. Juda then took them to his grave and dug up the body of Jesus. The Jewish leaders were greatly relieved and wanted to take the body. Juda replied that he would sell them the body of Jesus and did so for thirty pieces of silver. The Jewish priests then dragged Jesus' body through the streets of Jerusalem.” 
The weakness of this polemic was its lack of explanatory power. For, if the Jewish priests really did drag the body of Jesus through the streets of Jerusalem, then there would have been no way for Christianity to originate as it did through Jerusalem; it would have been completely falsified. Moreover, this account does not explain the experiences that the disciples claimed to have had of the risen Jesus.
Despite the low reliability of this passage, it does reflect an early Jewish polemic against Christianity that the disciples stole the body of Jesus. This polemic is expressed in Matthew 28:11-15, and is confirmed by Justin Martyr (AD 150) and Tertullian (AD 200). 
We might now consider some of the significant pagan sources that contain information about Jesus. Perhaps the most well-known of these sources is the early second century Roman historian, Tacitus. Regarding the fire of Rome, he writes:
“Consequently, to get rid of the report, Nero fastened the guilt and inflicted the most exquisite tortures on a class hated for their abominations, called Christians by the populace. Christus, from whom the name had its origin, suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilate, and a most mischievous superstition, thus checked for the moment, again broke out not only in Judaea, the first source of the evil, but even in Rome, where all things hideous and shameful from every part of the world find their centre and become popular. . . .” 
From this passage, we know that some of the earliest Christians were well-known and persecuted. We also know that Jesus (here called “Christus”) was the originator of this group, that he was put to death at the time the NT says he was, and that there was some supernatural belief Christians had about Jesus (resurrection?). The fact that Christianity spread so quickly to Rome may also be a confirmation of traditions about Peter and Paul, who traveled to Rome in order to evangelize. Fr. Pat correctly mentions that Tacitus was technically (and somewhat trivially) wrong about Pilate being a procurator, when in fact, he was a prefect. However, this would be like mentioning John McCain as a congressman, even though he is a Senator. This is one detail that can be easily overlooked.
Thallus is another source who is quoted by the third century Christian writer, Julius Africanus. Julius comments:
“On the whole world there pressed a most fearful darkness; and the rocks were rent by an earthquake, and many places in Judea and other districts were thrown down. This darkness Thallus, in the third book of his History, calls, as appears to me without reason, an eclipse of the sun.” 
Although there are no whole extant manuscripts of Thallus' work, Julius preserves this little slice from it. The objection that Julius had to the alternative explanation of Thallus was that an eclipse could not take place during the time of a full moon, as was the case during the Jewish Passover.  This has been commonly noted among popular apologists, who point out that non-Christians were trying to explain away an otherwise supernatural event by a naturalistic hypothesis. And, given the implausibility of the naturalistic hypothesis, they opt for a supernatural one.
One final pagan source to consider (and there are many others) is Pliny the Younger. Pliny was a government official who wrote around the year AD 112.  He explained:
“They (the Christians) were in the habit of meeting on a certain fixed day before it was light, when they sang in alternate verses a hymn to Christ, as to a god, and bound themselves by a solemn oath, not to any wicked deeds, but never to commit any fraud, theft or adultery, never to falsify their word, nor deny a trust when they should be called upon to deliver it up; after which it was their custom to separate, and then reassemble to partake of food – but food of an ordinary and innocent kind.” 
This text is very important, given that it testifies to many of the beliefs and practices of the early Christians. From this passage, we find more confirmation that the Christians believed Jesus to be divine, that they assembled and shared food (the Eucharist?), and had high moral standards.
All of these texts in some way help to confirm things we already know about Jesus from the NT. However, it is helpful to learn what the earliest counterparts to Christians knew about Jesus and his followers, and what they themselves believed. Even though they considered Christian beliefs to be superstitions, they acknowledge that these were the earliest beliefs, which is the first part to understanding the “real Jesus.” As Luke Timothy Johnson concludes, “These are all the notices concerning Jesus from outsiders that can arguably be said to rely on observation, rumor, and reports rather than on the direct reading of the New Testament writings themselves.”  If this is so, then we have some independent witness that the facts about Jesus contained within the NT are truly facts, and not merely fabricated by the NT writers. The multiplication of witnesses who agree on something attests to the truth about what they agree upon. Hence, we find some good starting points for discussion on what is true about Jesus.
 Gary Habermas, The Historical Jesus, College Press, 1996, p. 203.
 ibid., p. 203.
 ibid., p. 205.
 ibid., p. 205.
 ibid., p. 188.
 ibid., p. 196-197.
 ibid., p. 197.
 ibid., p. 198
 ibid., p. 199.
 Luke Timothy Johnson, The Real Jesus, HarperCollins Publishers, 1996, p. 116.