The commemoration of all the faithful departed is celebrated by the Church on 2 November, or, if this be a Sunday or a solemnity, on 3 November. The Office of the Dead must be recited by the clergy and all the Masses are to be of Requiem, except one of the current feast, where this is of obligation.
The theological basis for the feast is the doctrine that the souls which, on departing from the body, are not perfectly cleansed from venial sins, or have not fully atoned for past transgressions, are debarred from the Beatific Vision, and that the faithful on earth can help them by prayers, almsdeeds and especially by the sacrifice of the Mass. (See PURGATORY.)
@ Catholic Encyclopedia
Amy has devoted a post to prayer intentions. Check that out or leave them here in the comment box.