Last year our grade 8 math teachers held a math fair with their students, supported by the Galileo Educational Network. Students were introduced to a number of classic mathematical problems and brainteasers, and were allowed to choose what medium would best represent their solutions.
The Galileo site has a number of resources on math fairs, including lists of problems, and three different rubrics (here, here and here).
This student-created video solution was a response to the Babushka Squares problem. This video is exceptional in it’s clarity and depth. The student skillfully uses the medium of video (made on iMovie) to demonstrate how powerful student voice can be in demonstrating understanding in core curriculum areas: