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.
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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.