I have seen a project where the kids make a turkey body then make several colorful feathers. On each feather they write something they are thankful for.
But my favorite Thanksgiving writing piece is a persuasive paper that the kids write from the point of view of a turkey. They are to choose something else for people to eat for Thanksgiving, and convince us to eat that instead of them. The kids really get into it. I start with the book T'was the Day Before Thanksgiving and go from there. I have a template of a turkey holding a paper that I use as a header for the paper. Cute and fun, and I get surprisingly good papers out of it, especially for so early in the year.