One simple prayer to say at meal times is the basic Catholic prayer, which reads: "Bless us, Oh Lord, and these thy gifts, which we are about to receive, from thy bounty, through Christ, Our Lord. Amen." Another prayer comes from the Episcopal Book of Common Prayer and expands upon the first line of the Catholic prayer, and then ends with praising God and Jesus.
Most meal-time prayers begin with thanking God for the meal and blessing the food. The prayer may go on to praise God for other things as well. A Jewish meal time prayer begins with "Blessed art Thou, O Lord our God" and continues praising God for creating and sustaining every little thing. This prayer does not explicitly refer to food or a meal.
Celtic prayers such as "The Selkirk Grace" popularized by Robert Burns are often rhyming prayers. That particular prayer mentions those who want to eat, but have no food, or those who have food and cannot eat. It then refers to those gathered as both with food and desire to eat, and thus praising the Lord.
Another Irish prayer begins with blessing the food, then goes on to invite anyone walking along who may be hungry or thirsty to be brought to the table.