What does the Bible say about prayers of 'thanksgiving'?
Thanksgiving in an important part of Christian religion. Many prayers used in Christian churches involve thanking the Lord for various benefactions. This sense of thanksgiving is an inherent part of the Eucharistic ceremony, which is based, to a large degree, on the account of the last supper in Paul's 1st Epistle to the Corinthians, in which Jesus is portrayed as offering bread as a form of his own body:
And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me. (1 Cor 11:24)
Notice that Jesus gives thanks before distributing the bread. Many Christians still say "grace" before a meal to simultaneously thank God for the food before them and pray that they will use the gifts of God well and wisely, e.g. "For the bounty laid before us, may the Lord make us thankful, and ever mindful of the needs of others. Amen."
Several prayers of thanksgiving appear in the liturgy for harvest festivals ("Thanksgiving" in Canada and the United States) which may be found in Roman Catholic missals or the Anglican or Episcopalian Book of Common Prayer. These liturgies are based on biblical passages.