ExtraBiblical Documentation of Jesus' Life
 
Bertrand Russell famously said “Historically it is quite doubtful whether Christ ever existed at all, and if He did we do not know anything about Him.” (Why I am not a Christian). However, this position represents an extreme minority opinion among scholars who study this area, even among those who don't accept the resurrection. The reason is that, beyond the new testament documentation, there is an enormous amount of extrabiblical contemporary through 3rd century corroboration of the life of Jesus and the resulting religious movement. 

Below I've listed some of the more prominent extrabiblical references. Note that "Jesus" is the Anglicized version of the Jewish name "Yeshua" or "Yeshu;" and "Christ," "Christus," or "Christos," are the Greek versions of the Jewish term "Mashiach" meaning "Messiah."

Secular Sources:

TACITUS (55-120) writes a reference in Annals about "Christus" in his section describing Nero’s reign. 

SUETONIUS (ca70-ca130) refers to "Chrestus" in Life of Claudius, and Nero blaming Christians for setting the fire in Rome in Lives of the Caesars. 

PLINY THE YOUNGER (61-ca112) as governor of Bithynia writes in a letter to emperor Trajan for advice on whether to continue killing so many Christians or use further selection techniques since many seemed harmless. 

THALLUS (middle of first century) writes about an eclipse during Jesus’ execution (ms lost but quoted in Julius Africanus (late 2nd/early 3rd century).

PHLEGON (?80-?) in Chronicles also writes about this eclipse (ms also lost but quoted by Origen (185-254), Philopon, and Julius Africanus)

MARA BAR-SERAPION, in a letter from prison to his son (written some time after 70 CE), lists Jesus as another wrongfully executed leader along with Socrates and Pythagoras, and said their teachings lived on.

LUCIAN OF SAMOSATA (ca125-ca180), a Greek satirist, gives a scornful reference to Jesus in The Death of Peregrine.

Jewish Sources:

There are many of these. Some include the BABYLONIAN TALMUD description of Yeshu (or Yeshu the Nazarene) being hanged on the eve of the Passover for practicing sorcery and an allegation that he was illegitimate; and JOSEPHUS (37/38-after 100 CE) (2 references in his Jewish Antiquities).

Christian Sources:

There are also many who wrote and quoted extensively. Some include CLEMENT OF ROME (late first century), IGNATIUS (c35-c108), QUADRATUS (late first century-129 CE), ARISTIDES (second century CE), JUSTIN MARTYR (c. 100-165 CE), and HEGESIPPUS (110-180 CE).