In last night's section of "From Jesus to Christ", the program talked about the diversity within Judaism in Jesus' time. Even though there was only one Temple, in Jerusalem, where the One God lived, there were a number of sects and political parties arguing with each other about the right way to be a Jew.
When we read the gospels and hear Jesus arguing with Pharisees and Sadducees, this would have been well within the customs and traditions of the time. They all argued with each other, and a Rabbi would have been expected to be able to account for his teachings and interpretations. The disputes with Pharisees and Sadducees are not what got Jesus killed. His ability to stir up the common people made him a threat to Rome, which then made him a threat to the security of the Jewish nation.
Anyway, a quick rundown on these players, thanks to Ray Brown, author of An Introduction to the New Testament.
Pharisees: A non-priestly sect that taught obedience to the Law of Moses, and also to a second, orally transmitted Law of Moses. You could become holy in your daily life by living according to the Law. They believed in angels and in the resurrection from the dead. After the Temple was destroyed in 70 A.D., this style of Judaism that was not based in Temple sacrifices, allowed Judaism to survive and led to the synagogue style of Judaism practiced today.
Sadducees: A group aligned with the priests in the Temple and also with the ruling Jewish aristocracy (Herod, et. al.) Apparently, they did not believe in the resurrection from the dead.
Essenes: A group that became angry about changes in Temple worship. A group of Essenes fled Jerusalem to live in caves by the Dead Sea. The Dead Sea Scrolls reveal a settlement of Essenes living in strict, almost monastic, seclusion from 150 BC to 70 AD in this area. They had apocalyptic expectations and awaited two Messiahs to set things to rights: The Messiah of Aaron, who would sort out all the problems with Temple worship, and the Messiah of David, who would lead the war that would throw the Romans out for good.
Other sects: Sicarii and Zealots, and other rebels also played a role, although they seem to have been focused primarly on revolt and violent overthrow of the Roman rulers.
The scholars featured in "From Jesus to Christ" discuss this Jewish diversity here.