Most skeptics will not accept biblical sources when it comes to the existence of Jesus of Nazarth. They usually want extra-biblical (those sources outside of the Bible) sources with the thought that there will not be any or perhaps very few sources that make mention of Jesus. In order to show that this does nothing to support their case or their claims, below is a compiled list of non-Biblical historical sources dating between 30-180 years after Jesus lived.
Disciples of the Apostles:
Clement of Rome (mid to late 1st Century: knew Paul and John)
Papias (c. 60-130 A.D.: disciple of John and friend of Polycarp)
Polycarp (c. 69-156 A.D.: disciple of John and friend of Ignatius and Papias)
Ignatius (d. 107 A.D.: a friend of Polycarp and probably a disciple of John and possibly another apostle)
2nd Century Fathers:
Justin Martyr (c. 100-165 A.D.)
Irenaeus (d. 200 A.D.)
Apollonarius (2nd Century)
Aristides (early 2nd Century)
Athenagoras (late 2nd Century)
Clement of Alexandria (late 2nd Century)
Dionysius of Corinth (2nd Century)
Hegesippus (c. 110-180 A.D.)
Hermas (1st or 2nd Century: Origen believed him to be the Hermas of Romans 16:14)
Melito (d. c. 190 A.D.)
Tatian (mid to late 2nd Century)
Tertullian (late 2nd Century)
Theophilus (2nd Century)
Anonymous Works:
The Epistle of Barnabas (c. 70-100 A.D.)
Didache (c. 50-120 A.D.)
Critics of Christianity:
Celsus (2nd Century critic of Christianity)
Marcion (d. c. 160 A.D.)
Gnostic Writings:
The Gospel of Truth (c. 140-180 A.D.)
The Apocryphon of John (c. 120-180 A.D.)
The Gospel of Thomas (c. 50-140 A.D.)
The Treatise on the Resurrection (c. 170-200 A.D.)
Ancient Historians:
Cornelius Tacitus (c. 115 A.D.)
Suetonius (c. 115 A.D.)
Flavius Josephus (c. 93 A.D.)
Thallus (c. 52 A.D.)
Government Officials:
Pliny the Younger (c. 111-112 A.D.)
Emperor Trajan (early 2nd century)
Emperor Hadrian (early 2nd century)
Other Jewish Sources:
The Talmud (c. 135 A.D.)
Toledoth Jesu (Compiled in the 5th Century A.D., these were a collection of writings dating from mid 1st century to mid 2nd century A.D.)
Other Gentiles:
Lucian of Samosata (c. 165-175 A.D.)
Mara Bar-Serapion (c. 73-200 A.D.)
Other Sources behind the Gospels:
M (Sayings in Matthew only but not in other Gospels)
L (Sayings in Luke only but not in other Gospels)
Q (Sayings in both Matthew and Luke but not in other Gospels)