In the chinese lantern festival (coming up on February 6), children in China and in other areas across Asia, carry lanterns with riddles on them as they go into their temples. Here are some lesson plans and templates for making your own lanterns. You could have students put riddles on them relating to topics you have going in your classroom.
The Latin American Street Children's Organization has a math challenge that runs this Friday, February 3rd. Registration is open through January 31st. It is open to classrooms around the world. I find this interesting because the students debate the strategies for solving math problems. This is the largest math competition in Ireland but is spreading to other countries. When you participate, each child donates 1 british pound (convert to dollars for US) to participate. This looks like a fascinating competition and one that math teachers, particularly those who have students with Latin American heritage, may be excited to join.
This upcoming Friday is the UNICEF day for change in the UK but what a great idea. I can't find anything on the US website about this activity but it seems to be all over UK websites. I think that it is a great idea to have some sort of "change day" for children's activities in schools whether it is for UNICEF or another cause. Many students have change in their houses and can do something.