The seven sorrows of Mary, traditionally, are the following:
the prophecy of Simeon (a sword will pierce your soul);
the flight into Egypt;
having lost the Holy Child at Jerusalem;
meeting Jesus on his way to Calvary;
standing at the foot of the Cross;
Jesus being taken from the Cross;
the burial of Christ.
However, when we think of the sorrows of Mary we think primarily of her standing at the foot of the Cross. One of the most beautiful hymns of the Middle Ages commemorates this, and I've provided a link to it. You can read the hymn in Latin and English, and also hear it sung.