From New Bible Commentary, 21st Century Edition,  Ed.: D.A.Carson, R.T. France, J.A. Motyer, G.J. Wenham. (p, 1012.)

The Sadducees were a Jewish group, chiefly drawn from the priesthood and the wealthy aristocracy, who were perfectly happy with the existing situation under Roman rule.  They had a traditional, conservative type of religion which was based on the five books of Moses, but it was empty and formal.  Unlike the Pharisees, they accepted only the material world and denied the resurrection, angels and spirits.

(From Drane, J. Introducing the New Testament, p.34-37)

The Jewish historian Josephus, who lived towards the end of the first century AD, and who was a friend of the Romans, tells us that three main opinions were common among the Jews in Palestine: 'Jewish philospohy takes three forms.  The followers of the first school are called Pharisees, of the second Sadducees, and the third sect, which has a reputation of being more disciplined, is the Essenes.'......

The Sadducees are often mentioned along with the Pharisees, but in fact the two groups were quite separate and held opposite opinions on almost everything.  The Sadducees were only a small group, but they were very influential......They were extreme conservatives in everything and disliked changes of any kind, epecially changes which could affect their own dominant position in society.

If the Sadducees are to be regarded as political conservatives, their understanding of the Jewish religion can only be called reactionary. They held that the only religious teaching with any authority was the Law given by Moses in the first five books of the Old Testament (the Pentateuch or Torah).  They had no time either for the rest of the Old Testament, or for anyone who tried to reinterpret it or to apply it in a more direct way to their own situation........ Sadducees did not believe that God had a purpose behind the events of history, and matters such as belief in a future life, resurrection, or a final judgement were to them simply irrelevant.

The Pharisees were a much larger group......Many of these were professional students of the Old Testament, but others had ordinary jobs.  They were a national organization, with a large number of local groups.....  Religiously, they were probably the most important people in Judaism during Jesus' lifetime.  The Sadducees disliked them because they believed and did things that a literal understanding of the Law of Moses could not really allow.  But most ordinary people had a great respect for them.

....they had amassed a whole lot of rules and regulations to explain the Law of the Old Testament.
(They surrounded the Law with) cautionary rules to act as a warning notice to stop people before they get within breaking distance of the God-given Law itself.  This intention was praiseworthy enough.  But there can be no doubt that eventually it led the Pharisees to make so many absurd rules that the Law became a moral millstone to the pious rather than a gift from God.

Jesus denounced them as hypocrites.  He could see that the keeping of their own sectarian rules and regulations had become far too important.

Like many others since, they came to equate knowing God with being a member of their group - a Pharisee.  To be a member of the sect was ultimately more important than knowing and understanding the will of God himself.  Though they often claimed to be keeping God's Law, they were in fact only drawing attention to their own moral achievements.

(from p 252)

Pharisees believed that history had a goal and a purpose.  They held that God was ordering events according to his own plan, which would culminate in the coming of a Messiah to lead his people.

Pharisees believed in a future life.

Pharisees believed in the existence of angels and demons.  The Sadducees did not.