This little box for the "pièces jaunes" (small change) appears next to cash registers all over Paris in January. It's fun for children, who can pick up the box for free at the Post Office as a flat puzzle, assemble it, then fill it during the month from 6 January to 11 February. They are requested not to ask for money in the street or from their neighbors! Even though they don't get anything out of it, there is an unofficial competition to fill the boxes.
Once the box is full, they bring it to the post office between January 30th and February 11th, where the money is collected and counted by the Bank of France and used to improve the quality of life of children in hospitals. Last year, 5.6 million euros was collected this way.
I always get one of the little boxes too. It's a good way to use up those little coins that accumulate at home.