PBS
Pbs Frontline: The Mystery and Meaning of the Dead Sea Scrolls
A great introduction to the scrolls, how found, their importance to Judaism and Christianity, and the historical circumstances surrounding their origins (who wrote them, etc.).
Wikimedia
Wikipedia: Sadducee
Although not much is known about the Sadducees, this encyclopedia article discusses some of their beliefs as attributed by other sources.
Other
What You Never Knew About the Pharisees
This site discusses the roles that the Sadducees and Pharisees played in society during Jesus' lifetime.
Other
Christian Library: Jewish Sects
This site presents in outline form the three major sects that appeared during the time of Jesus, and how these sects affected the Jewish people as a whole.
New Advent
Catholic Encyclopedia: Pharisees
This site from The New Advent extensively delves into the historical and religious significance of the politico-religious sect of ancient Judaism known as Pharisaism. Please note that ?The Catholic Encyclopedia? is a historic reference...
New Advent
Catholic Encyclopedia: The Essenes
This site thoroughly details the known history and religious significance of the ancient Jewish sect, the Essenes. Please note that ?The Catholic Encyclopedia? is a historic reference source and should be viewed in the context of...