The Noon Day project - students measure shadows to find out what the
circumference of the earth is. (That is what Eratosthenes did in Egypt 2200
years ago.)
Warm up: The Pizza Slice Problem

The Million Three-cube Roll Race - Predict who will win! Middle school
students will contribute to the race by rolling 3 dice 100 times and posting
their results on the Internet. The goal will be to reach a million rolls.
(Can we do it?)

Warm Up:  the one and two cube roll games.
 
The Great Green Globs contest - Students will try to get the best score by
"shooting down" globs on a coordinate X Y axis by entering in equations.
Lesson: Everything You Ever Wanted to Know about Equations, Lines, Slopes, and Graphs but Were Afraid to Ask

You can find out more about these and other activities on the CIESEmath Website:
http://www.ciese.org/ciesemath