Orthodox Chrisitans do not believe that all of humankind inherits the guilt of Adam's sin as the Catholics do. We believe in the 'fallen nature' - that Adam, by sinning, has corrupted human nature and we are born into a nature of sin.
Orthodox Christians accept Mary as the ever-Virgin Mother of God. We do not believe that she had other children. The passages that speak of Jesus' "brethren" or "brothers" can have two meanings. 1) Aramaic had no word for 'cousin' so the word 'brother' was used. There are many examples in the Bible where the word 'brother' does not mean actual biological brotherhood. 2) Jesus' "brethren" were St. Joseph's children from a previous marriage. He was an old man when he married Mary, and the marriage was only for security, for Mary was a Temple Virgin. There was to be no sexual relations between them. Orthodox Christians do not worship Mary or believe that she is God. We venerate her as the person that God chose to become incarnate from. We ask her to pray for us before her Son, Jesus Christ our God, in heaven.
Yes, the Orthodox Church does believe that Jesus is divine. The Trinity is a fundamental dogma in Orthodoxy, the rejection of which makes one a heretic. However, the Orthodox believe that the Holy Spirit proceeds from the Father only, whereas Catholics and Protestants believe that the Holy Spirit proceeds from the Father and the Son.
The main differences between the Orthodox and Roman Catholic churches are:
1) The Papacy - Catholics believe that the Pope is the head of the entire Church, the Orthodox believe that all Bishops are equal and that no Bishop has any power outside of his own jurisdiction. The Pope is a "Super-Bishop" according to the Catholic Church.
2) The procession of the Holy Spirit - Orthodox believe that the Holy Spirit proceeds only from the Father (which is Scriptural - see John 15:26), while the Catholic Church believes that the Holy Spirit proceeds from both the Father and the Son. They illicitly added this to the Creed when they had no authority to do so.
3) Married clergy - Catholic priests are required to be celibate. Orthodox priests (but not Bishops) may be married.
4) Hell - the Orthodox Church believes that sinners who hate God will be tormented by being forever in His presence. The Roman Catholic Church believes that hell is a literal place of fire and brimstone.
There are many more differences, and you can read about them here:
http://ocab.netfirms.com/romancatholic.htm