This year I gave the students the option of contributing cash that I would match and purchase gifts for our family. We made this paper chain to remind students to bring in cash and to be proud of the contribution they made.
When a student gives me money they get a red or green link for each dollar as well blue links to represent my matching dollar. The paper chain gives them a visual of how much impact one dollar makes to our overall project. It also provides a bit of festive decor.
Does your mentor (homeroom) group do anything similar for the holidays? How do you encourage student participation in your service projects?