First Day Activity using Post-It Notes. What are your goals for this year? How will you reach these goals? What can (the teacher) do to help you this year? This could be adapted for high school students.
A quick get to know you/math (counting and graphing) activity. Later in the year students can generate the questions and write them. Place on light colored paper, laminate, and questions can be added with white board marker.
Have students bring in any food box or item to hang up on the board, then have them figure out in coins how much each costs. This is very helpful for young students who are just learning about the value of money.