In the Orthodox Tradition, he is known not for his doubt, but for his wonderful confession of faith "My Lord and My God!" when he came face to face with the risen Savior. It is a pious custom in the West to confess as did St Thomas "My Lord and My God" when the priest presents the Body and Blood of Christ in the Eucharist.
The Lord commended Thomas for his faith, and furthermore blessed those in the generations to come saying "Blessed are they that do not see, and yet believe."
Holy Apostle Thomas, by your intercession to Christ our God, may our faith be strengthened and may our souls be saved. Amen.