• Using Statistics by Travers, Stout, Swift, and Sextro. Addison-Wesley Publishing Company. 1985.
  I first heard of this problem from Dr. Kenneth Travers. You can find a discussion of the cereal box problem and other expected value problems in this book.

• The Cereal Box Problem by Jesse Wilkins. In preparation.
  This paper has an elaboration of the mathematics behind this problem. It should be available soon (probably in Mathematics Teacher).

• Fun With Probability by Mike Cornell This is an activity on the same problem. Check it out! He also has downloadable materials (worksheets and Excel files) in addition to data collected from several schools.

There are also several good activities on probability available through the MSTE Mathematics Lessons and Software Database. Choose "probability" as the content area and do the search.