Nearly every major religious group has prayers for the dead including Christians, Jews, Muslims, Buddhists and Hindus. Various sects of each faith often have differing prayers. In particular, Christian prayers for the dead vary greatly; there are different practices in Catholic, Eastern Orthodox and Protestant traditions.
In the Catholic tradition, there is a specific "Prayer for the Dead" which is said alongside the Our Father, Hail Mary and Glory Be prayers. The Catholic prayers for the dead are intertwined with Catholic notion of purgatory, a state of suffering where souls atone for their sins before going to heaven. Prayers for the dead were supposed to help relieve their suffering sooner. The oft-quoted prayer "May the souls of all the faithful departed, through the mercy of God, rest in peace" is a portion of the "Prayer for the Poor Souls in Purgatory."
In contrast, Eastern Orthodox Christians do not have a doctrine of purgatory but still have prayers that are supposed to help the deceased. Eastern Orthodox traditions have a prayer for each stage in the death process including the "Prayers at the Departure of the Soul" at the moment of death and "Panikhidas" (prayer services) that involve reading the "Prayer of the Hours,"" Memory Eternal" and hymns every day for the next 40 days.
In the Methodist Faith, when a person dies a "Service of Death and Resurrection" is held in their honor. At this service, a pastor will read the Memorial Acclamation, which is a prayer for the dead that begins "Dying, Christ destroyed our death/ Rising, Christ restored our life." Readings from Psalms are also heard, often including Psalms 23 or 130.