For the last five years, I have had my students make 100 day glasses. These are super easy to make as I have a template that I simply trace on manila folders. The students decorate the glasses, cut them out, and then get to wear them all day long. This year I also found some fun and simple worksheets online that I put together into a booklet to celebrate the 100th day of school.
The kids loved making these glasses and wearing them all.day.long.